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  • 151. Order onlineBuy this publication >>
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    The HiPIMS Process2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis involves experimental and theoretical studies related to a thin film deposition technique called high power impulse magnetron sputtering (HiPIMS), and more specifically the plasma properties and how they influence the coating. HiPIMS is an ionized physical vapor deposition technique based on conventional direct current magnetron sputtering (DCMS). The major difference between the two methods is that HiPIMS has the added advantage of providing substantial ionization of the sputtered material, and thus presents many new opportunities for the coating industry. Understanding the dynamics of the charged species and their effect on thin film growth in the HiPIMS process is therefore essential for producing high-quality coatings.

    In the first part of the thesis a new type of anomalous electron transport was found. Investigations of the transport resulted in the discovery that this phenomenon could quantitatively be described as being related and mediated by highly nonlinear waves, likely due to the modified two-stream instability, resulting in electric field oscillations in the MHz-range (the lower hybrid frequency). Measurements in the plasma confirmed these oscillations as well as trends predicted by the theory of these types of waves. Using electric probes, the degree of anomalous transport in the plasma could also be determined by measuring the current density ratio between the azimuthal current density (of which the Hall current density is one contribution) and the discharge current density, Jϕ / JD. The results were verified in another series of measurements using Rogowski probes to directly gain insight into the internal currents in the HiPIMS discharge. The results provided important insights into understanding the mechanism behind the anomalous transport.

    It was furthermore demonstrated that the current ratio Jϕ / JD is inversely proportional to the transverse resistivity, η , which governs how well momentum in the direction of the current is transferred from the electrons to the ions in the plasma. By looking at the forces involved in the charged particle transport it was expected that the azimuthally rotating electrons would exert a volume force on the ions tangentially outwards from the circular race track region. The effect of having an anomalous transport would therefore be that the ions were transported across the magnetic field lines and to a larger extent deflected sideways, instead of solely moving from the target region towards a substrate placed in front of the target some distance away. From the experiments it was confirmed that a substantial fraction of sputtered material is transported radially away from the cathode and lost to the walls in HiPIMS as well as in DCMS, but more so for HiPIMS giving one possible explanation to why the deposition rate is lower for HiPIMS compared to DCMS. Moreover, in a separate investigation on the energy flux it could be determined that the heating due to radial energy flux reached as much as 60 % of the axial energy flux, which is likely a result of the anomalous transport of charged species present in the HiPIMS discharge. Also, the recorded ion energy flux confirmed theoretical estimations on this type of transport regarding energy and direction.In order to gain a better understanding of the complete discharge regime, as well as providing a link between the HiPIMS and DCMS processes, the current and voltage characteristics were investigated for discharge pulses longer than 100 μs. The current behavior was found to be strongly correlated with the chamber gas pressure. Based on these experiments it was suggested that high-current transients commonly seen in the HiPIMS process cause a depletion of the working gas in the area in front of the target, and thereby a transition to a DCMS-like high voltage, lower current regime, which alters the deposition conditions.

    In the second part of the thesis, using the results and ideas from the fundamental plasma investigations, it was possible to successfully implement different coating improvements. First, the concept of sideways deposition of thin films was examined in a dual-magnetron system providing a solution for coating complex shaped surfaces. Here, the two magnetrons were facing each other having opposing magnetic fields forcing electrons, and thereby also ionized material to be transported radially towards the substrate. In this way deposition inside tubular substrates can be made in a beneficial way.

    Last, the densification process of thin films using HiPIMS was investigated for eight different materials (Al, Ti, Cr, Cu, Zr, Ag, Ta, and Pt). Through careful characterization of the thin film properties it was determined that the HiPIMS coatings were approximately 5-15 % denser compared to the DCMS coatings. This could be attributed to the increased ion bombardment seen in the HiPIMS process, where the momentum transfer between the growing film and the incoming ions is very efficient due to the equal mass of the atoms constituting the film and the bombarding species, leading to a less pronounced columnar microstructure. The deposition conditions were also examined using a global plasma model, which was in good agreement with the experimental results.

    List of papers
    1. Anomalous electron transport in high power impulse magnetron sputtering
    Open this publication in new window or tab >>Anomalous electron transport in high power impulse magnetron sputtering
    Show others...
    2008 (English)In: Plasma Sources Science and Technology, ISSN 0963-0252, Vol. 17, no 2, p. 025007-Article in journal (Refereed) Published
    Abstract [en]

    Oscillating electric fields in the megahertz range have been studied in a high power impulse magnetron sputtering (HIPIMS) plasma with the use of electric field probe arrays. One possible reason for these oscillations to occur is charge perturbation—or so-called modified two-stream instabilities (MTSIs). It is known that MTSIs give rise to acceleration of the charged plasma species and can give a net transport of electrons across the magnetic field lines. Measurements of these oscillations confirm trends, specifically of the frequency dependence on ion mass and magnetic field strength as expected from the theory of MTSI waves. These results help to explain the previously reported anomalous fast electron transport in HIPIMS discharges, where classical theory of diffusion using collisions to transport electrons has failed.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13208 (URN)10.1088/0963-0252/17/2/025007 (DOI)
    Note
    Original Publication: Daniel Lundin, Ulf Helmersson, Scott Kirkpatrick, Suzanne Rohde and Nils Brenning, Anomalous electron transport in high power impulse magnetron sputtering, 2008, Plasma Sources Science and Technology, (17), 2, 025007. http://dx.doi.org/10.1088/0963-0252/17/2/025007 Copyright: IOP Publishing http://www.iop.org/ Available from: 2009-02-22 Created: 2009-02-17 Last updated: 2013-10-30Bibliographically approved
    2. Cross-field ion transport during high power impulse magnetron sputtering
    Open this publication in new window or tab >>Cross-field ion transport during high power impulse magnetron sputtering
    Show others...
    2008 (English)In: Plasma Sources Science and Technology, ISSN 0963-0252, Vol. 17, no 035021Article in journal (Refereed) Published
    Abstract [en]

    In this study, the effect on thin film growth due to an anomalous electron transport, found in high power impulse magnetron sputtering (HiPIMS), has been investigated for the case of a planar circular magnetron. An important consequence of this type of transport is that it affects the way ions are being transported in the plasma. It was found that a significant fraction of ions are transported radially outwards in the vicinity of the cathode, across the magnetic field lines, leading to increased deposition rates directly at the side of the cathode (perpendicular to the target surface). Furthermore, this mass transport parallel to the target surface leads to that the fraction of sputtered material reaching a substrate placed directly in front of the target is substantially lower in HiPIMS compared with conventional direct current magnetron sputtering (dcMS). This would help to explain the lower deposition rates generally observed for HiPIMS compared with dcMS. Moreover, time-averaged mass spectrometry measurements of the energy distribution of the cross-field transported ions were carried out. The measured distributions show a direction-dependent high-energy tail, in agreement with predictions of the anomalous transport mechanism.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13209 (URN)10.1088/0963-0252/17/3/035021 (DOI)
    Note
    Original Publication: Daniel Lundin, Petter Larsson, Erik Wallin, Martina Lattemann, Nils Brenning and Ulf Helmersson, Cross-field ion transport during high power impulse magnetron sputtering, 2008, Plasma Sources Science and Technology, (17), 035021. http://dx.doi.org/10.1088/0963-0252/17/3/035021 Copyright: Iop Publishing http://www.iop.org/ Available from: 2009-02-26 Created: 2009-02-26 Last updated: 2013-10-30Bibliographically approved
    3. Transition between the discharge regimes of high power impulse magnetron sputtering and conventional direct current magnetron sputtering
    Open this publication in new window or tab >>Transition between the discharge regimes of high power impulse magnetron sputtering and conventional direct current magnetron sputtering
    Show others...
    2009 (English)In: PLASMA SOURCES SCIENCE and TECHNOLOGY, ISSN 0963-0252, Vol. 18, no 4, p. 045008-Article in journal (Refereed) Published
    Abstract [en]

    Current and voltage have been measured in a pulsed high power impulse magnetron sputtering (HiPIMS) system for discharge pulses longer than 100 mu s. Two different current regimes could clearly be distinguished during the pulses: (1) a high-current transient followed by (2) a plateau at lower currents. These results provide a link between the HiPIMS and the direct current magnetron sputtering (DCMS) discharge regimes. At high applied negative voltages the high-current transient had the characteristics of HiPIMS pulses, while at lower voltages the plateau values agreed with currents in DCMS using the same applied voltage. The current behavior was found to be strongly correlated with the chamber gas pressure, where increasing gas pressure resulted in increasing peak current and plateau current. Based on these experiments it is suggested here that the high-current transients cause a depletion of the working gas in the area in front of the target, and thereby a transition to a DCMS-like high-voltage, lower current regime.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-51382 (URN)10.1088/0963-0252/18/4/045008 (DOI)
    Available from: 2009-10-30 Created: 2009-10-30 Last updated: 2015-05-28
    4. Energy flux measurements in high power impulse magnetron sputtering
    Open this publication in new window or tab >>Energy flux measurements in high power impulse magnetron sputtering
    2009 (English)In: JOURNAL OF PHYSICS D-APPLIED PHYSICS, ISSN 0022-3727, Vol. 42, no 18, p. 185202-Article in journal (Refereed) Published
    Abstract [en]

    The total energy flux in a high power impulse magnetron sputtering (HiPIMS) plasma has been measured using thermal probes. Radial flux (parallel to the magnetron surface) as well as axial flux (perpendicular to the magnetron surface) were measured at different positions, and resulting energy flux profiles for the region between the magnetron and the substrate are presented. It was found that the substrate heating is reduced in the HiPIMS process compared with conventional direct current magnetron sputtering (DCMS) at the same average power. On the other hand, the energy flux per deposited particle is higher for HiPIMS compared with DCMS, when taking into account the lower deposition rate for pulsed sputtering. This is most likely due to the highly energetic species present in the HiPIMS plasma. Furthermore, the heating due to the radial energy flux reached as much as 60% of the axial energy flux, which is likely a result of the anomalous transport of charged species present in the HiPIMS discharge. Finally, the experimental results were compared with theoretical calculations on energy flux of charged species and were found to be in good agreement.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-20748 (URN)10.1088/0022-3727/42/18/185202 (DOI)
    Available from: 2009-09-18 Created: 2009-09-18 Last updated: 2015-05-28
    5. Internal current measurements in high power impulse magnetron sputtering
    Open this publication in new window or tab >>Internal current measurements in high power impulse magnetron sputtering
    Show others...
    2011 (English)In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 20, no 4, p. 045003-Article in journal (Refereed) Published
    Abstract [en]

    The transport of charged particles in a high power impulse magnetron sputtering (HiPIMS) discharge is of great interest when optimizing this promising deposition technique with respect to deposition rate and control of the ion acceleration. In this study the internal current densities Jϕ (azimuthal direction) and JD⊥ (axial direction) have therefore been spatially and temporally resolved in the bulk plasma region above a cylindrical magnetron using Rogowski coils. From the measurements a phenomenological model has been constructed describing the evolution of the current density in this pulsed plasma. The core of the model is based on six different types of current systems, which characterize the operating transport mechanisms, such as current transport along and across magnetic field lines, as well as the initiation, buildup and steady-state of a HiPIMS plasma. Furthermore, the data also shows that there are spatial and temporal variations of the key transport parameter Jϕ/JD⊥ , governing the cross-B resistivity and also the energy of the charged particles. The previously reported faster-than-Bohm cross-B electron transport is here verified, but is not found to be present during the whole discharge regime as well as for all locations. These results on the plasma dynamics are essential input when modeling the axial electric field, governing the back-attraction of ionized sputtered material, and might furthermore provide a link between the different resistivities reported in HiPIMS, pulsed-DC, and DC magnetron discharges.

    Place, publisher, year, edition, pages
    Institute of Physics, 2011
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-56743 (URN)10.1088/0963-0252/20/4/045003 (DOI)000295829800005 ()
    Note
    Funding agencies|Swedish Research Council||Swedish Foundation for Strategic Research||Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12
    6. Dual-magnetron open field sputtering system for sideways deposition of thin films
    Open this publication in new window or tab >>Dual-magnetron open field sputtering system for sideways deposition of thin films
    2010 (English)In: SURFACE and COATINGS TECHNOLOGY, ISSN 0257-8972, Vol. 204, no 14, p. 2165-2169Article in journal (Refereed) Published
    Abstract [en]

    A dual-magnetron system for deposition inside tubular substrates has been developed. The two magnetrons are facing each other and have opposing magnetic fields forcing electrons and thereby also ionized material to be transported radially towards the substrate. The depositions were made employing direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS). To optimize the deposition rate, the system was characterized at different separation distances between the magnetrons under the same sputtering conditions. The deposition rate is found to increase with increasing separation distance independent of discharge technique. The emission spectrum from the HiPIMS plasma shows a highly ionized fraction of the sputtered material. The electron densities of the order of 10(16) m(-3) and 10(18) m(-3) have been determined in the DCMS and the HiPIMS plasma discharges respectively. The results demonstrate a successful implementation of the concept of sideways deposition of thin films providing a solution for coating complex shaped surfaces.

    Keywords
    Dual-magnetron, Open field configuration, Sideways deposition, HiPIMS, HPPMS, DCMS
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-54766 (URN)10.1016/j.surfcoat.2009.11.044 (DOI)000275920900009 ()
    Available from: 2010-04-09 Created: 2010-04-09 Last updated: 2015-05-28
    7. On the film density using high power impulse magnetron sputtering
    Open this publication in new window or tab >>On the film density using high power impulse magnetron sputtering
    Show others...
    2010 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 205, no 2, p. 591-596Article in journal (Refereed) Published
    Abstract [en]

    The influence on thin film density using high power impulse magnetron sputtering (HIPIMS) has been investigated for eight different target materials (Al, Ti, Cr. Cu, Zr, Ag, Ta, and Pt). The density values as well as deposition rates have been compared to results obtained from thin films grown by direct current magnetron sputtering (DCMS) under the same experimental conditions. Overall, it was found that the HIPIMS deposited coatings were approximately 5-15% denser compared to the DCMS deposited coatings This could be attributed to the increased metal ion bombardment commonly seen in HIPIMS discharges, which also was verified using a global plasma model to assess the degree of ionization of sputtered metal One key feature is that the momentum transfer between the growing film and the incoming metal ions is very efficient due to the equal mass of film and bombarding species, leading to a less pronounced columnar microstructure As expected the deposition rates were found to be lower for HiPIMS compared to DCMS For several materials this decrease is not as pronounced as previously reported in the literature, which is shown in the case of Ta. Pt, and Ag with rate(HIPIMS)/rate(DCMS)-70-85%. while still achieving denser coatings

    Place, publisher, year, edition, pages
    Elsevier Science B.V., Amsterdam., 2010
    Keywords
    HIPIMS, HPPMS, DCMS, Density, RBS, Global plasma model
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-60690 (URN)10.1016/j.surfcoat.2010.07.041 (DOI)000282542300053 ()
    Available from: 2010-11-01 Created: 2010-10-22 Last updated: 2017-12-12Bibliographically approved
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    The HiPIMS Process
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    Cover
  • 152.
    Lundin, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Al Sahab, Seham
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Brenning, Nils
    Division of Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    Huo, Chunqing
    Division of Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Internal current measurements in high power impulse magnetron sputtering2011In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 20, no 4, p. 045003-Article in journal (Refereed)
    Abstract [en]

    The transport of charged particles in a high power impulse magnetron sputtering (HiPIMS) discharge is of great interest when optimizing this promising deposition technique with respect to deposition rate and control of the ion acceleration. In this study the internal current densities Jϕ (azimuthal direction) and JD⊥ (axial direction) have therefore been spatially and temporally resolved in the bulk plasma region above a cylindrical magnetron using Rogowski coils. From the measurements a phenomenological model has been constructed describing the evolution of the current density in this pulsed plasma. The core of the model is based on six different types of current systems, which characterize the operating transport mechanisms, such as current transport along and across magnetic field lines, as well as the initiation, buildup and steady-state of a HiPIMS plasma. Furthermore, the data also shows that there are spatial and temporal variations of the key transport parameter Jϕ/JD⊥ , governing the cross-B resistivity and also the energy of the charged particles. The previously reported faster-than-Bohm cross-B electron transport is here verified, but is not found to be present during the whole discharge regime as well as for all locations. These results on the plasma dynamics are essential input when modeling the axial electric field, governing the back-attraction of ionized sputtered material, and might furthermore provide a link between the different resistivities reported in HiPIMS, pulsed-DC, and DC magnetron discharges.

    Download full text (pdf)
    fulltext
  • 153.
    Lundin, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Brenning, Nils
    Royal Institute of Technology.
    Jädernäs, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Larsson, Petter
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Wallin, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Lattemann, Martina
    Tech University of Darmstadt.
    Raadu, Michael A
    Royal Institute Technology.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Transition between the discharge regimes of high power impulse magnetron sputtering and conventional direct current magnetron sputtering2009In: PLASMA SOURCES SCIENCE and TECHNOLOGY, ISSN 0963-0252, Vol. 18, no 4, p. 045008-Article in journal (Refereed)
    Abstract [en]

    Current and voltage have been measured in a pulsed high power impulse magnetron sputtering (HiPIMS) system for discharge pulses longer than 100 mu s. Two different current regimes could clearly be distinguished during the pulses: (1) a high-current transient followed by (2) a plateau at lower currents. These results provide a link between the HiPIMS and the direct current magnetron sputtering (DCMS) discharge regimes. At high applied negative voltages the high-current transient had the characteristics of HiPIMS pulses, while at lower voltages the plateau values agreed with currents in DCMS using the same applied voltage. The current behavior was found to be strongly correlated with the chamber gas pressure, where increasing gas pressure resulted in increasing peak current and plateau current. Based on these experiments it is suggested here that the high-current transients cause a depletion of the working gas in the area in front of the target, and thereby a transition to a DCMS-like high-voltage, lower current regime.

    Download full text (pdf)
    fulltext
  • 154.
    Lundin, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Kirkpatrick, Scott
    University of Nebraska-Lincoln.
    Rohde, Suzanne
    University of Nebraska-Lincoln.
    Brenning, Nils
    Royal Institute of Technology, Stockholm.
    Anomalous electron transport in high power impulse magnetron sputtering2008In: Plasma Sources Science and Technology, ISSN 0963-0252, Vol. 17, no 2, p. 025007-Article in journal (Refereed)
    Abstract [en]

    Oscillating electric fields in the megahertz range have been studied in a high power impulse magnetron sputtering (HIPIMS) plasma with the use of electric field probe arrays. One possible reason for these oscillations to occur is charge perturbation—or so-called modified two-stream instabilities (MTSIs). It is known that MTSIs give rise to acceleration of the charged plasma species and can give a net transport of electrons across the magnetic field lines. Measurements of these oscillations confirm trends, specifically of the frequency dependence on ion mass and magnetic field strength as expected from the theory of MTSI waves. These results help to explain the previously reported anomalous fast electron transport in HIPIMS discharges, where classical theory of diffusion using collisions to transport electrons has failed.

    Download full text (pdf)
    FULLTEXT01
  • 155.
    Lundin, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Kirkpatrick, Scott
    University of Nebraska.
    Brenning, Nils
    KTH.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Anomalous electron transport in high power impulse magnetron sputtering plasmas2007In: International Vacuum Congress,2007, 2007Conference paper (Other academic)
  • 156.
    Lundin, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Larsson, Petter
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Wallin, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Lattemann, Martina
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Brenning, Nils
    Royal Institute of Technology, Stockholm.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Cross-field ion transport during high power impulse magnetron sputtering2008In: Plasma Sources Science and Technology, ISSN 0963-0252, Vol. 17, no 035021Article in journal (Refereed)
    Abstract [en]

    In this study, the effect on thin film growth due to an anomalous electron transport, found in high power impulse magnetron sputtering (HiPIMS), has been investigated for the case of a planar circular magnetron. An important consequence of this type of transport is that it affects the way ions are being transported in the plasma. It was found that a significant fraction of ions are transported radially outwards in the vicinity of the cathode, across the magnetic field lines, leading to increased deposition rates directly at the side of the cathode (perpendicular to the target surface). Furthermore, this mass transport parallel to the target surface leads to that the fraction of sputtered material reaching a substrate placed directly in front of the target is substantially lower in HiPIMS compared with conventional direct current magnetron sputtering (dcMS). This would help to explain the lower deposition rates generally observed for HiPIMS compared with dcMS. Moreover, time-averaged mass spectrometry measurements of the energy distribution of the cross-field transported ions were carried out. The measured distributions show a direction-dependent high-energy tail, in agreement with predictions of the anomalous transport mechanism.

    Download full text (pdf)
    FULLTEXT01
  • 157.
    Lundin, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    High power pulsed plasma enhanced chemical vapor deposition: a brief overview of general concepts and early results2013In: NINETEENTH EUROPEAN CONFERENCE ON CHEMICAL VAPOR DEPOSITION (EUROCVD 19), 2013, Vol. 46, p. 3-11Conference paper (Refereed)
    Abstract [en]

    The general concepts of the emerging plasma enhanced chemical vapor deposition (PECVD) technique High Power Pulsed PECVD (HiPP-PECVD) are outlined; the main feature of HiPP-PECVD is the use of a power scheme characterized by high power pulses with a duty cycle of a few percent or less to generate a process plasma with a significantly higher plasma density compared to traditional PECVD. The higher plasma density leads to a more reactive plasma chemistry, which results in a higher rate of dissociation of the precursor molecules, i.e. a more efficient use of the source material. The high plasma density also leads to a higher degree of ionization of the growth species, enabling the possibility to guide the growth species to the substrate or applying an energetic bombardment of the growing film by applying a substrate bias. Early results on HiPP-PECVD have shown that HiPP-PECVD enables deposition of phase pure alpha-Al2O3 at substrate temperatures as low as 560 degrees C with mechanical properties comparable to standard thermal CVD grown material. Also, deposition of amorphous, copper containing carbon films at deposition rates higher than 30 mu m/h has been demonstrated together with results showing the more efficient plasma chemistry. It is suggested that HiPPPECVD is a promising tool for low temperature deposition of films with tailored properties for e.g. the hard coatings industry. (C) 2013 The Authors. Published by Elsevier B.V.

  • 158.
    Lundin, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    An introduction to thin film processing using high-power impulse magnetron sputtering2012In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 27, no 5, p. 780-792Article, review/survey (Refereed)
    Abstract [en]

    High-power impulse magnetron sputtering (HiPIMS) is a promising sputtering-based ionized physical vapor deposition technique and is already making its way to industrial applications. The major difference between HiPIMS and conventional magnetron sputtering processes is the mode of operation. In HiPIMS the power is applied to the magnetron (target) in unipolar pulses at a low duty factor (andlt;10%) and low frequency (andlt;10 kHz) leading to peak target power densities of the order of several kilowatts per square centimeter while keeping the average target power density low enough to avoid magnetron overheating and target melting. These conditions result in the generation of a highly dense plasma discharge, where a large fraction of the sputtered material is ionized and thereby providing new and added means for the synthesis of tailor-made thin films. In this review, the features distinguishing HiPIMS from other deposition methods will be addressed in detail along with how they influence the deposition conditions, such as the plasma parameters and the sputtered material, as well as the resulting thin film properties, such as microstructure, phase formation, and chemical composition. General trends will be established in conjunction to industrially relevant material systems to present this emerging technology to the interested reader.

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    fulltext
  • 159.
    Lundin, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Stahl, Marc
    University of Kiel.
    Kersten, Holger
    University of Kiel.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Energy flux measurements in high power impulse magnetron sputtering2009In: JOURNAL OF PHYSICS D-APPLIED PHYSICS, ISSN 0022-3727, Vol. 42, no 18, p. 185202-Article in journal (Refereed)
    Abstract [en]

    The total energy flux in a high power impulse magnetron sputtering (HiPIMS) plasma has been measured using thermal probes. Radial flux (parallel to the magnetron surface) as well as axial flux (perpendicular to the magnetron surface) were measured at different positions, and resulting energy flux profiles for the region between the magnetron and the substrate are presented. It was found that the substrate heating is reduced in the HiPIMS process compared with conventional direct current magnetron sputtering (DCMS) at the same average power. On the other hand, the energy flux per deposited particle is higher for HiPIMS compared with DCMS, when taking into account the lower deposition rate for pulsed sputtering. This is most likely due to the highly energetic species present in the HiPIMS plasma. Furthermore, the heating due to the radial energy flux reached as much as 60% of the axial energy flux, which is likely a result of the anomalous transport of charged species present in the HiPIMS discharge. Finally, the experimental results were compared with theoretical calculations on energy flux of charged species and were found to be in good agreement.

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    fulltext
  • 160.
    Lü, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Dynamics of the Early Stages in Metal-on-Insulator Thin Film Deposition2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thin films consist of nanoscale layers of material that are used in many technological applications to either functionalize a surface or serve as parts in miniaturized devices. The properties of a film are closely related to its microstructure, which in turn can be tuned during film preparation. Thin film growth involves a multitude of atomic-scale processes that cannot always be easily studied experimentally. Therefore, different types of computer simulations have been developed in order to test theoretical models of thin film growth in a highly controlled way. To be able to compare simulation and experimental results, the simulations must be able to model events on experimental time-scales, i.e. several seconds or minutes. This is achievable with the kinetic Monte Carlo method.

    In this work, kinetic Monte Carlo simulations are used to model the initial growth stages of metal films on insulating, amorphous substrates. This includes the processes of island nucleation, three-dimensional island growth and island coalescence. Both continuous and pulsed vapor fluxes are investigated as deposition sources, and relations between deposition parameters and film morphology are formulated. Specifically, the film thickness at what is known as the “elongation transition” is studied as a function of the temporal profile of the vapor flux, adatom diffusivity and the coalescence rate. Since the elongation transition occurs due to hindrance of coalescence completion, two separate scaling behaviors of the elongation transition film thickness are found: one where coalescence occurs frequently and one where coalescence occurs infrequently. In the latter case, known nucleation behaviors can be used favorably to control the morphology of thin films, as these behaviors are not erased by island coalescence. Experimental results of Ag growth on amorphous SiO2 that confirm the existence of these two “growth regimes” are also presented for both pulsed and continuous deposition by magnetron sputtering. Knowledge of how to avoid coalescence for different deposition conditions allows nucleation for metal-on-insulator material systems to be studied and relevant physical quantities to be determined in a way not previously possible. This work also aids understanding of the growth evolution of polycrystalline films, which in conjunction with advanced deposition techniques allows thin films to be tailored to specific applications.

    List of papers
    1. Unravelling the Physical Mechanisms that Determine Microstructural Evolution of Ultrathin Volmer-Weber Films
    Open this publication in new window or tab >>Unravelling the Physical Mechanisms that Determine Microstructural Evolution of Ultrathin Volmer-Weber Films
    2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, no 4, p. 044302-Article in journal (Refereed) Published
    Abstract [en]

    The initial formation stages (i.e., island nucleation, island growth, and island coalescence) set characteristic length scales during growth of thin films from the vapour phase. They are, thus, decisive for morphological and microstructural features of films and nanostructures. Each of the initial formation stages has previously been well-investigated separately for the case of Volmer-Weber growth, but knowledge on how and to what extent each stage individually and all together affect the microstructural evolution is still lacking. Here we address this question using growth of Ag on SiO2 from pulsed vapour fluxes as a case study. By combining in situ growth monitoring, ex situ imaging and growth simulations we systematically study the growth evolution all the way from nucleation to formation of a continuous film and establish the effect of the vapour flux time domain on the scaling behaviour of characteristic growth transitions (elongation transition, percolation and continuous film formation). Our data reveal a pulsing frequency dependence for the characteristic film growth transitions, where the nominal transition thickness decreases with increasing pulsing frequency up to a certain value after which a steady-state behaviour is observed. The scaling behaviour is shown to result from differences in island sizes and densities, as dictated by the initial film formation stages. These differences are determined solely by the interplay between the characteristics of the vapour flux and time required for island coalescence to be completed. In particular, our data provide evidence that the steady-state scaling regime of the characteristic growth transitions is caused by island growth that hinders coalescence from being completed, leading to a coalescence-free growth regime.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-103920 (URN)10.1063/1.4890522 (DOI)000340710700078 ()
    Available from: 2014-02-03 Created: 2014-02-03 Last updated: 2018-01-11
    2. Dynamic competition between island growth and coalescence in metal-on-insulator deposition
    Open this publication in new window or tab >>Dynamic competition between island growth and coalescence in metal-on-insulator deposition
    2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 16, p. 163107-1-163107-5Article in journal (Refereed) Published
    Abstract [en]

    The morphology of thin metal films and nanostructures synthesized from the vapor phase on insulating substrates is strongly influenced by the coalescence of islands. Here, we derive analytically the quantitative criterion for coalescence suppression by combining atomistic nucleation theory and a classical model of coalescence. Growth simulations show that using this criterion, a coalescence-free growth regime can be reached in which morphological evolution is solely determined by island nucleation, growth, and impingement. Experimental validation for the ability to control the rate of coalescence using this criterion and navigate between different growth regimes is provided by in situ monitoring of Ag deposition on SiO2. Our findings pave the way for creating thin films and nanostructures that exhibit a wide range of morphologies and physical attributes in a knowledge-based manner.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2014
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-112133 (URN)10.1063/1.4900575 (DOI)000344363000073 ()
    Available from: 2014-11-17 Created: 2014-11-17 Last updated: 2018-01-11Bibliographically approved
    3. Growth regimes during metal-on-insulator deposition using pulsed vapor fluxes
    Open this publication in new window or tab >>Growth regimes during metal-on-insulator deposition using pulsed vapor fluxes
    2014 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The morphology and physical properties of thin films deposited by vapor condensation on solid surfaces are predominantly set by the initial surface processes of nucleation, island growth and coalescence. When deposition is performed using pulsed vapor fluxes, three distinct nucleation regimes are known to exist depending on the temporal profile of the flux. While these regimes can be accessed by tuning deposition conditions, their effect on film microstructure becomes marginal when coalescence sets in and erases morphological features obtained during nucleation. By preventing coalescence from being completed, these nucleation regimes can be used in a straightforward manner to control microstructure evolution and thus access a larger palette of film morphological features. Recently, we proposed a mechanism and derived the quantitative criterion to stop coalescence during continuous vapor flux deposition, based on a competition between island growth by atomic incorporation and the coalescence rate of islands [Lü et al., Appl. Phys. Lett. 105, 163107 (2014)]. In the present study, we develop the analytical framework for entering a coalescence-free growth regime for thin film deposition using pulse vapor fluxes, showing that there exist three distinct criteria corresponding to the three nucleation regimes of pulsed vapor flux deposition. The theoretical framework developed herein is substantiated by kinetic Monte Carlo growth simulations. Our findings highlight the possibility of using classical nucleation theory for pulsed vapor deposition to design materials which have an inherent tendency to coalesce.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-112134 (URN)
    Available from: 2014-11-17 Created: 2014-11-17 Last updated: 2014-11-17Bibliographically approved
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    Dynamics of the Early Stages in Metal-on-Insulator Thin Film Deposition
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  • 161.
    Lü, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Growth and characterization of HfON thin films with the crystal structures of HfO22011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    HfO2 is a popular replacement for SiO2 in modern CMOS technology. It is used as the gate dielectric layer isolating the transistor channel from the gate. For this application, certain material property demands need to be met, most importantly, a high static dielectric constant is desirable as this positively influences the effectiveness and reliability of the device. Previous theoretical calculations have found that this property varies with the crystal structure of HfO2; specifically, the tetragonal structure possesses the highest dielectric constant (~70 from theoretical calculations) out of all possible stable structures at atmospheric pressure, with the cubic phase a far second (~29, also calculated). Following the results from previous experimental work on the phase formation of sputtered HfO2, this study investigates the possibility of producing thin films of HfO2 with the cubic or tetragonal structure by the addition of nitrogen to a reactive sputtering process at various deposition temperatures. Also, a new physical vapor deposition method known as High Power Impulse Magnetron Sputtering (HiPIMS) is employed for its reported deposition stability in the transition zone of metal-oxide compounds and increased deposition rate. Structural characterization of the produced films shows that films deposited at room temperature with a low N content (~6 at%) are mainly composed of amorphous HfO2 with mixed crystallization into t-HfO2 and c-HfO2, while pure HfO2 is found to be composed of amorphous HfO2 with signs of crystallization into m-HfO2. At 400o C deposition temperature, the crystalline quality is enhanced and the structure of N incorporated HfO2 is found to be c-HfO2 only, due to further ordering of atoms in the crystal lattice. Optical and dielectric characterization revealed films with low N incorporation (< 6 at%) to be insulating while these became conductive for higher N contents. For the insulating films, a trend of increasing static dielectric constant with increasing N incorporation is found.

    Download full text (pdf)
    Growth and characterization of HfON thin films with the crystal structures of HfO2
  • 162.
    Lü, Bo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Elofsson, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Dynamic competition between island growth and coalescence in metal-on-insulator deposition2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 16, p. 163107-1-163107-5Article in journal (Refereed)
    Abstract [en]

    The morphology of thin metal films and nanostructures synthesized from the vapor phase on insulating substrates is strongly influenced by the coalescence of islands. Here, we derive analytically the quantitative criterion for coalescence suppression by combining atomistic nucleation theory and a classical model of coalescence. Growth simulations show that using this criterion, a coalescence-free growth regime can be reached in which morphological evolution is solely determined by island nucleation, growth, and impingement. Experimental validation for the ability to control the rate of coalescence using this criterion and navigate between different growth regimes is provided by in situ monitoring of Ag deposition on SiO2. Our findings pave the way for creating thin films and nanostructures that exhibit a wide range of morphologies and physical attributes in a knowledge-based manner.

    Download full text (pdf)
    fulltext
  • 163.
    Lü, Bo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Münger, E. Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Growth regimes during metal-on-insulator deposition using pulsed vapor fluxes2014Manuscript (preprint) (Other academic)
    Abstract [en]

    The morphology and physical properties of thin films deposited by vapor condensation on solid surfaces are predominantly set by the initial surface processes of nucleation, island growth and coalescence. When deposition is performed using pulsed vapor fluxes, three distinct nucleation regimes are known to exist depending on the temporal profile of the flux. While these regimes can be accessed by tuning deposition conditions, their effect on film microstructure becomes marginal when coalescence sets in and erases morphological features obtained during nucleation. By preventing coalescence from being completed, these nucleation regimes can be used in a straightforward manner to control microstructure evolution and thus access a larger palette of film morphological features. Recently, we proposed a mechanism and derived the quantitative criterion to stop coalescence during continuous vapor flux deposition, based on a competition between island growth by atomic incorporation and the coalescence rate of islands [Lü et al., Appl. Phys. Lett. 105, 163107 (2014)]. In the present study, we develop the analytical framework for entering a coalescence-free growth regime for thin film deposition using pulse vapor fluxes, showing that there exist three distinct criteria corresponding to the three nucleation regimes of pulsed vapor flux deposition. The theoretical framework developed herein is substantiated by kinetic Monte Carlo growth simulations. Our findings highlight the possibility of using classical nucleation theory for pulsed vapor deposition to design materials which have an inherent tendency to coalesce.

  • 164. Macak, K.
    et al.
    Kouznetsov, V.
    Schneider, Jochen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Petrov, I.
    Materials Science Department, Materials Research Laboratory, University of Illinois, Urbana, IL 61801, United States.
    Ionized sputter deposition using an extremely high plasma density pulsed magnetron discharge2000In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 18, no 4 II, p. 1533-1537Article in journal (Refereed)
    Abstract [en]

    A high power density pulsed plasma discharge for ionized sputter deposition is studied. The temporal evolution of the plasma ion composition in high power pulsed magnetron sputtering is investigated and shows that Ar ions dominated the beginning of the pulse. As time elapsed, metal ions are detected and finally dominated the ion composition.

  • 165. Order onlineBuy this publication >>
    Magnfält, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Fundamental processes in thin film growth: The origin of compressive stress and the dynamics of the early growth stages2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The fundamental mechanisms behind the generation of compressive stresses in polycrystalline thin films, the effects of pulsed deposition fluxes on the dynamics of the early growth stages as well as the generation of energetic Ar+ ions in high power impulse magnetron sputtering (HiPIMS) discharges has been studied in this thesis.

    It was found that compressive film stresses in Mo films deposited using energetic vapor fluxes are correlated with high film densities while only a slight lattice expansion compared to relaxed Mo was found. This implies that the stress is caused by grain boundary densification and not defect creation in the grain bulk. The compressive stress magnitude should scale with the grain boundary length per unit area, or the inverse grain size, if the stress originates in the grain boundaries. This was found to be the case for dense Mo films confirming that the observed compressive stresses originate in the grain boundaries. Similarly to what has been suggested for conditions where adatoms are highly mobile we suggest that atom insertion into grain boundaries is the cause of the compressive stresses observed in the Mo films.

    Island nucleation, growth and coalescence are the dynamic processes that decide the initial microstructure of thin films growing in a three dimensional fashion. Using Ag on SiO2 as a model system and estimations of adatom life times and coalescence time it was shown that the time scales of island nucleation and coalescence are in the same range as the time scale of the vapor flux modulation in HiPIMS and other pulsed deposition methods. In situ real time measurements were used to demonstrate that it is possible to decrease the thickness at which a continuous film is formed from 21 to 15 nm by increasing the flux modulation frequency. A more in depth study where in situ real time monitoring was coupled with ex situ imaging and kinetic Monte Carlo simulations showed that this behavior is due to the interplay of the pulsed deposition flux and island coalescence where island coalescence is hindered at high pulsing frequencies.

    The generation of energetic Ar+ ions was investigated by ion mass spectrometry and Monte Carlo simulations of gas transport. It was shown that the energetic Ar+ ions originate from Ar atoms backscattered from the target that are ionized in the plasma by correlating the length of the high energy tail in the ion energy distribution functions with the atomic mass of the Cr, Mo and W sputtering targets. 

    List of papers
    1. Atom insertion into grain boundaries and stress generation in physically vapor deposited films
    Open this publication in new window or tab >>Atom insertion into grain boundaries and stress generation in physically vapor deposited films
    2013 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 5Article in journal (Refereed) Published
    Abstract [en]

    We present evidence for compressive stress generation via atom insertion into grain boundaries in polycrystalline Mo thin films deposited using energetic vapor fluxes (<∼120 eV). Intrinsic stress magnitudes between −3 and +0.2 GPa are obtained with a nearly constant stress-free lattice parameter marginally larger (0.12%) than that of bulk Mo. This, together with a correlation between large compressive film stresses and high film densities, implies that the compressive stress is not caused by defect creation in the grains but by grain boundary densification. Two mechanisms for diffusion of atoms into grain boundaries and grain boundary densification are suggested.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-98154 (URN)10.1063/1.4817669 (DOI)000322723000036 ()
    Note

    Funding Agencies|COST Action|MP0804|Linkoping University.

    The previous status of this article was Manuscript and the working title was Atomistic mechanisms leading to adatom insertion into grain boundaries and stress generation in physically vapor deposited films.

    Available from: 2013-09-30 Created: 2013-09-30 Last updated: 2017-12-06
    2. Compressive intrinsic stress originates in the grain boundaries of dense refractory polycrystalline thin films
    Open this publication in new window or tab >>Compressive intrinsic stress originates in the grain boundaries of dense refractory polycrystalline thin films
    Show others...
    2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 5, p. 055305-Article in journal (Refereed) Published
    Abstract [en]

    Intrinsic stresses in vapor deposited thin films have been a topic of considerable scientific and technological interest owing to their importance for functionality and performance of thin film devices. The origin of compressive stresses typically observed during deposition of polycrystalline metal films at conditions that result in high atomic mobility has been under debate in the literature in the course of the past decades. In this study, we contribute towards resolving this debate by investigating the grain size dependence of compressive stress magnitude in dense polycrystalline Mo films grown by magnetron sputtering. Although Mo is a refractory metal and hence exhibits an intrinsically low mobility, low energy ion bombardment is used during growth to enhance atomic mobility and densify the grain boundaries. Concurrently, the lateral grain size is controlled by using appropriate seed layers on which Mo films are grown epitaxially. The combination of in situ stress monitoring with ex situ microstructural characterization reveals a strong, seemingly linear, increase of the compressive stress magnitude on the inverse grain size and thus provides evidence that compressive stress is generated in the grain boundaries of the film. These results are consistent with models suggesting that compressive stresses in metallic films deposited at high homologous temperatures are generated by atom incorporation into and densification of grain boundaries. However, the underlying mechanisms for grain boundary densification might be different from those in the present study where atomic mobility is intrinsically low. (C) 2016 AIP Publishing LLC.

    Place, publisher, year, edition, pages
    AMER INST PHYSICS, 2016
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-125810 (URN)10.1063/1.4941271 (DOI)000369900600028 ()
    Note

    Funding Agencies|COST Action "Highly Ionized Pulsed Plasmas" [MP0804]; Swedish Research Council VR [621-2014-4882]; Linkoping University via the "LiU Research Fellows" program.

    The previous status of this article was Manuscript and the working title was Atom insertion into grain boundaries generates compressive intrinsic stress in polycrystalline thin films.

    Available from: 2016-03-08 Created: 2016-03-04 Last updated: 2017-11-30Bibliographically approved
    3. Time-domain and energetic bombardment effects on the nucleation and coalescence of thin metal films on amorphous substrates
    Open this publication in new window or tab >>Time-domain and energetic bombardment effects on the nucleation and coalescence of thin metal films on amorphous substrates
    Show others...
    2013 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 46, no 21, article id 215303Article in journal (Refereed) Published
    Abstract [en]

    Pulsed, ionized vapour fluxes, generated from high power impulse magnetron sputtering (HiPIMS) discharges, are employed to study the effects of time-domain and energetic bombardment on the nucleation and coalescence characteristics during Volmer–Weber growth of metal (Ag) films on amorphous (SiO2) substrates. In situ monitoring of the film growth, by means of wafer curvature measurements and spectroscopic ellipsometry, is used to determine the film thickness where a continuous film is formed. This thickness decreases from ~210 to ~140 Å when increasing the pulsing frequency for a constant amount of material deposited per pulse or when increasing the amount of material deposited per pulse and the energy of the film forming species for a constant pulsing frequency. Estimations of adatom lifetimes and the coalescence times show that there are conditions at which these times are within the range of the modulation of the vapour flux. Thus, nucleation and coalescence processes can be manipulated by changing the temporal profile of the vapour flux. We suggest that other than for elucidating the atomistic mechanisms that control pulsed growth processes, the interplay between the time scales for diffusion, coalescence and vapour flux pulsing can be used as a tool to determine characteristic surface diffusion and island coalescence parameters.

    Place, publisher, year, edition, pages
    Institute of Physics (IOP), 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-95508 (URN)10.1088/0022-3727/46/21/215303 (DOI)000319116300009 ()
    Note

    Funding Agencies|Swedish Research Council|VR 621-2011-4280|COST Action Highly Ionized Pulsed Plasmas|MP0804|Linkoping University via the LiU Research Fellows program||.

    The previous status of the article was Manuscript and the working title was Time-domain and energetic bombardment effects on the nucleation and post-nucleation characteristics during none-quilibrium film synthesis.

    Available from: 2013-07-05 Created: 2013-07-05 Last updated: 2017-12-06Bibliographically approved
    4. Unravelling the Physical Mechanisms that Determine Microstructural Evolution of Ultrathin Volmer-Weber Films
    Open this publication in new window or tab >>Unravelling the Physical Mechanisms that Determine Microstructural Evolution of Ultrathin Volmer-Weber Films
    2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, no 4, p. 044302-Article in journal (Refereed) Published
    Abstract [en]

    The initial formation stages (i.e., island nucleation, island growth, and island coalescence) set characteristic length scales during growth of thin films from the vapour phase. They are, thus, decisive for morphological and microstructural features of films and nanostructures. Each of the initial formation stages has previously been well-investigated separately for the case of Volmer-Weber growth, but knowledge on how and to what extent each stage individually and all together affect the microstructural evolution is still lacking. Here we address this question using growth of Ag on SiO2 from pulsed vapour fluxes as a case study. By combining in situ growth monitoring, ex situ imaging and growth simulations we systematically study the growth evolution all the way from nucleation to formation of a continuous film and establish the effect of the vapour flux time domain on the scaling behaviour of characteristic growth transitions (elongation transition, percolation and continuous film formation). Our data reveal a pulsing frequency dependence for the characteristic film growth transitions, where the nominal transition thickness decreases with increasing pulsing frequency up to a certain value after which a steady-state behaviour is observed. The scaling behaviour is shown to result from differences in island sizes and densities, as dictated by the initial film formation stages. These differences are determined solely by the interplay between the characteristics of the vapour flux and time required for island coalescence to be completed. In particular, our data provide evidence that the steady-state scaling regime of the characteristic growth transitions is caused by island growth that hinders coalescence from being completed, leading to a coalescence-free growth regime.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-103920 (URN)10.1063/1.4890522 (DOI)000340710700078 ()
    Available from: 2014-02-03 Created: 2014-02-03 Last updated: 2018-01-11
    5. Origin of energetic Ar+ ions in high power impulse magnetron sputtering discharges
    Open this publication in new window or tab >>Origin of energetic Ar+ ions in high power impulse magnetron sputtering discharges
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Fusion, Plasma and Space Physics
    Identifiers
    urn:nbn:se:liu:diva-105790 (URN)
    Available from: 2014-04-07 Created: 2014-04-07 Last updated: 2014-04-08
    Download full text (pdf)
    Fundamental processes in thin film growth: The origin of compressive stress and the dynamics of the early growth stages
    Download (pdf)
    omslag
  • 166. Order onlineBuy this publication >>
    Magnfält, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Nucleation and stress generation in thin films deposited with a pulsed energetic deposition flux2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents fundamental mechanisms of nucleation and early growth of and stress generation in thin polycrystalline metal films deposited using pulsed energetic deposition fluxes. The effects of a pulsed deposition flux and energetic bombardment on film nucleation was investigated using in situ stress measurements and in situ ellipsometry to determine the film thickness at which the films become continuous. Ag films where deposited using high power impulse magnetron sputtering (HiPIMS) in two series - one with constant low pulse power to minimize energetic bombardment while varying the pulse frequency and one with a constant pulse frequency while varying the pulse power, resulting in different amounts of energetic bombardment and different deposition rates - to separate the effects of a pulsed deposition flux and energetic bombardment. The thickness at which the film becomes continuous was found to decrease both with increasing pulse frequency and increasing pulse power. The effects of the increased energetic bombardment and deposition rate cannot be separated due to their coupling. Adatom lifetimes and the coalescence times for islands where calculated for different coverages and island sizes and compared to the time between pulses. It was found that the time between pulses was lower than the adatom lifetimes for certain conditions; this leads to an increase in the adatom density and therefore an increase of the nucleation density resulting in smaller thicknesses for the formation of continuous film. It was also found that the coalescence time for clusters becomes longer than the time between pulses, retarding the coalescence process; this leads to formation of long lived elongated clusters also resulting in a decrease of the thickness at which the films become continuous.

    Energetic bombardment during growth of Mo films using HiPIMS is found to result in large compressive stresses without the commonly observed defect induced associated lattice expansion seen when depositing films using energetic bombardment. This and a correlation between the magnitude of the compressive stress and the film density allow us to conclude that the compressive stress is generated by grain boundary densification. Two mechanisms leading to grain boundary densification and thus generation of compressive stresses are proposed.

    List of papers
    1. Time-domain and energetic bombardment effects on the nucleation and coalescence of thin metal films on amorphous substrates
    Open this publication in new window or tab >>Time-domain and energetic bombardment effects on the nucleation and coalescence of thin metal films on amorphous substrates
    Show others...
    2013 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 46, no 21, article id 215303Article in journal (Refereed) Published
    Abstract [en]

    Pulsed, ionized vapour fluxes, generated from high power impulse magnetron sputtering (HiPIMS) discharges, are employed to study the effects of time-domain and energetic bombardment on the nucleation and coalescence characteristics during Volmer–Weber growth of metal (Ag) films on amorphous (SiO2) substrates. In situ monitoring of the film growth, by means of wafer curvature measurements and spectroscopic ellipsometry, is used to determine the film thickness where a continuous film is formed. This thickness decreases from ~210 to ~140 Å when increasing the pulsing frequency for a constant amount of material deposited per pulse or when increasing the amount of material deposited per pulse and the energy of the film forming species for a constant pulsing frequency. Estimations of adatom lifetimes and the coalescence times show that there are conditions at which these times are within the range of the modulation of the vapour flux. Thus, nucleation and coalescence processes can be manipulated by changing the temporal profile of the vapour flux. We suggest that other than for elucidating the atomistic mechanisms that control pulsed growth processes, the interplay between the time scales for diffusion, coalescence and vapour flux pulsing can be used as a tool to determine characteristic surface diffusion and island coalescence parameters.

    Place, publisher, year, edition, pages
    Institute of Physics (IOP), 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-95508 (URN)10.1088/0022-3727/46/21/215303 (DOI)000319116300009 ()
    Note

    Funding Agencies|Swedish Research Council|VR 621-2011-4280|COST Action Highly Ionized Pulsed Plasmas|MP0804|Linkoping University via the LiU Research Fellows program||.

    The previous status of the article was Manuscript and the working title was Time-domain and energetic bombardment effects on the nucleation and post-nucleation characteristics during none-quilibrium film synthesis.

    Available from: 2013-07-05 Created: 2013-07-05 Last updated: 2017-12-06Bibliographically approved
    2. Atom insertion into grain boundaries and stress generation in physically vapor deposited films
    Open this publication in new window or tab >>Atom insertion into grain boundaries and stress generation in physically vapor deposited films
    2013 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 5Article in journal (Refereed) Published
    Abstract [en]

    We present evidence for compressive stress generation via atom insertion into grain boundaries in polycrystalline Mo thin films deposited using energetic vapor fluxes (<∼120 eV). Intrinsic stress magnitudes between −3 and +0.2 GPa are obtained with a nearly constant stress-free lattice parameter marginally larger (0.12%) than that of bulk Mo. This, together with a correlation between large compressive film stresses and high film densities, implies that the compressive stress is not caused by defect creation in the grains but by grain boundary densification. Two mechanisms for diffusion of atoms into grain boundaries and grain boundary densification are suggested.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-98154 (URN)10.1063/1.4817669 (DOI)000322723000036 ()
    Note

    Funding Agencies|COST Action|MP0804|Linkoping University.

    The previous status of this article was Manuscript and the working title was Atomistic mechanisms leading to adatom insertion into grain boundaries and stress generation in physically vapor deposited films.

    Available from: 2013-09-30 Created: 2013-09-30 Last updated: 2017-12-06
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    Nucleation and stress generation in thin films deposited with a pulsed energetic deposition flux
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  • 167.
    Magnfält, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Abadias, G
    University of Poitiers, France.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Atom insertion into grain boundaries and stress generation in physically vapor deposited films2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 5Article in journal (Refereed)
    Abstract [en]

    We present evidence for compressive stress generation via atom insertion into grain boundaries in polycrystalline Mo thin films deposited using energetic vapor fluxes (<∼120 eV). Intrinsic stress magnitudes between −3 and +0.2 GPa are obtained with a nearly constant stress-free lattice parameter marginally larger (0.12%) than that of bulk Mo. This, together with a correlation between large compressive film stresses and high film densities, implies that the compressive stress is not caused by defect creation in the grains but by grain boundary densification. Two mechanisms for diffusion of atoms into grain boundaries and grain boundary densification are suggested.

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    fulltext
  • 168.
    Magnfält, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Elofsson, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Abadias, G
    Institut P', Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS-ENSMA, SP2MI, Téléport 2, Bd M. et P. Curie, F-86962 Chasseneuil-Futuroscope, France.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Time-domain and energetic bombardment effects on the nucleation and coalescence of thin metal films on amorphous substrates2013In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 46, no 21, article id 215303Article in journal (Refereed)
    Abstract [en]

    Pulsed, ionized vapour fluxes, generated from high power impulse magnetron sputtering (HiPIMS) discharges, are employed to study the effects of time-domain and energetic bombardment on the nucleation and coalescence characteristics during Volmer–Weber growth of metal (Ag) films on amorphous (SiO2) substrates. In situ monitoring of the film growth, by means of wafer curvature measurements and spectroscopic ellipsometry, is used to determine the film thickness where a continuous film is formed. This thickness decreases from ~210 to ~140 Å when increasing the pulsing frequency for a constant amount of material deposited per pulse or when increasing the amount of material deposited per pulse and the energy of the film forming species for a constant pulsing frequency. Estimations of adatom lifetimes and the coalescence times show that there are conditions at which these times are within the range of the modulation of the vapour flux. Thus, nucleation and coalescence processes can be manipulated by changing the temporal profile of the vapour flux. We suggest that other than for elucidating the atomistic mechanisms that control pulsed growth processes, the interplay between the time scales for diffusion, coalescence and vapour flux pulsing can be used as a tool to determine characteristic surface diffusion and island coalescence parameters.

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  • 169.
    Magnfält, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Fillon, A.
    University of Poitiers, France; INSA Rennes, France.
    Boyd, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Abadias, G.
    University of Poitiers, France.
    Compressive intrinsic stress originates in the grain boundaries of dense refractory polycrystalline thin films2016In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 5, p. 055305-Article in journal (Refereed)
    Abstract [en]

    Intrinsic stresses in vapor deposited thin films have been a topic of considerable scientific and technological interest owing to their importance for functionality and performance of thin film devices. The origin of compressive stresses typically observed during deposition of polycrystalline metal films at conditions that result in high atomic mobility has been under debate in the literature in the course of the past decades. In this study, we contribute towards resolving this debate by investigating the grain size dependence of compressive stress magnitude in dense polycrystalline Mo films grown by magnetron sputtering. Although Mo is a refractory metal and hence exhibits an intrinsically low mobility, low energy ion bombardment is used during growth to enhance atomic mobility and densify the grain boundaries. Concurrently, the lateral grain size is controlled by using appropriate seed layers on which Mo films are grown epitaxially. The combination of in situ stress monitoring with ex situ microstructural characterization reveals a strong, seemingly linear, increase of the compressive stress magnitude on the inverse grain size and thus provides evidence that compressive stress is generated in the grain boundaries of the film. These results are consistent with models suggesting that compressive stresses in metallic films deposited at high homologous temperatures are generated by atom incorporation into and densification of grain boundaries. However, the underlying mechanisms for grain boundary densification might be different from those in the present study where atomic mobility is intrinsically low. (C) 2016 AIP Publishing LLC.

  • 170.
    Magnfält, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Fillon, Amelié
    Institut P’, Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS- ENSMA.
    Boyd, Robert D.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Abadias, Gregory
    Institut P’, Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS- ENSMA.
    Atom insertion into grain boundaries generates compressive intrinsic stress in polycrystalline thin filmsManuscript (preprint) (Other academic)
  • 171.
    Magnfält, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Lundin, Daniel
    Laboratoire the Physique de Gaz et Plasmas, UMR 8578 CNRS, Universite Paris-Sud XI.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Minea, Tiberiu
    Laboratoire the Physique de Gaz et Plasmas, UMR 8578 CNRS, Universite Paris-Sud XI.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Origin of energetic Ar+ ions in high power impulse magnetron sputtering dischargesManuscript (preprint) (Other academic)
  • 172.
    Magnfält, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Melander, E.
    Uppsala University, Sweden.
    Boyd, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Kapaklis, V.
    Uppsala University, Sweden.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Synthesis of tunable plasmonic metal-ceramic nanocomposite thin films by temporally modulated sputtered fluxes2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 17, article id 171918Article in journal (Refereed)
    Abstract [en]

    The scientific and technological interest for metal-dielectric nanocomposite thin films emanates from the excitation of localized surface plasmon resonances (LSPRs) on the metal component. The overall optical response of the nanocomposite is governed by the refractive index of the dielectric matrix and the properties of the metallic nanoparticles in terms of their bulk optical properties, size, and shape, and the inter-particle distance of separation. In order to tune the film morphology and optical properties, complex synthesis processes which include multiple steps-i. e., film deposition followed by post-deposition treatment by thermal or laser annealing-are commonly employed. In the present study, we demonstrate that the absorption resonances of Ag/AlOxNy nanocomposite films can be effectively tuned from green (similar to 2.4 eV) to violet (similar to 2.8 eV) using a single-step synthesis process that is based on modulating the arrival pattern of film forming species with sub-monolayer resolution, while keeping the amount of Ag in the films constant. Our data indicate that the optical response of the films is the result of LSPRs on isolated Ag nanoparticles that are seemingly shifted by dipolar interactions between neighboring particles. The synthesis strategy presented may be of relevance for enabling integration of plasmonic nanocomposite films on thermally sensitive substrates. Published by AIP Publishing.

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  • 173. Order onlineBuy this publication >>
    Mickan, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Deposition of Al-doped ZnO films by high power impulse magnetron sputtering2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Transparent conducting oxides (TCOs) are an important class of materials with many applications such as low emissivity coatings, or transparent electrodes for photovoltaics and flat panel displays. Among the possible TCO materials, Al-doped ZnO (AZO) is studied due to its relatively low cost and abundance of the raw materials. Thin films of AZO are commonly produced using physical vapour deposition techniques such as magnetron sputtering. However, there is a problem with the homogeneity of the films using reactive direct current magnetron sputtering (DCMS). This homogeneity problem can be related to the bombardment of the growing film with negative oxygen ions, that can cause additional acceptor defects and the formation of insulating secondary phases. In this work AZO films are deposited by high power impulse magnetron sputtering (HiPIMS), a technique in which high instantaneous current densities are achieved by short pulses of low duty cycle.

    In the first part of this thesis, the possibility to improve the homogeneity of the deposited AZO films by using HiPIMS is demonstrated. This improvement can be related to the high instantaneous sputtering rate during the HiPIMS pulses, so the process can take place in the metal mode. This allows for a lower oxygen ion bombardment of the growing film, which can help to avoid the formation of secondary phases. Another problem of AZO is the stability of the properties in humid environments. To assess this problem, the degradation of the electrical properties after an aging procedure was investigated for films deposited by both DCMS and by HiPIMS. A method was proposed, to restore the properties of the films, using a low temperature annealing under N2 atmosphere. The improvement of the electrical properties of the films could be related to a diffusion process, where water is diffusing out of the films. Then, the influence of the substrate temperature on the properties of AZO films deposited by HiPIMS was studied. The electrical, optical and structural properties were found to improve with increasing substrate temperature up to 600 C. This improvement can be mostly explained by the increase in crystalline quality and the annealing of defects. Finally, the deposition of AZO films on flexible PET substrates was investigated. The films are growing as a thick porous layer of preferentially c-axis oriented columns on top of a thin dense seed layer. The evolution of the sheet resistance of the films after bending the films with different radii was studied. There is an increase in the sheet resistance of the films with decreasing bending radius, that is less pronounced for thicker films.

    List of papers
    1. Room temperature deposition of homogeneous, highly transparent and conductive Al-doped ZnO films by reactive high power impulse magnetron sputtering
    Open this publication in new window or tab >>Room temperature deposition of homogeneous, highly transparent and conductive Al-doped ZnO films by reactive high power impulse magnetron sputtering
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    2016 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 157, p. 742-749Article in journal (Refereed) Published
    Abstract [en]

    Aluminum doped zinc oxide (AZO) films have been deposited using reactive high power impulse magnetron sputtering (HiPIMS) and reactive direct current (DC) magnetron sputtering from an alloyed target without thermal assistance. These films have been compared in terms of their optical, electrical and structural properties. While both DC and HiPIMS deposited films show comparable transmittance, their electrical properties are significantly improved by the HiPIMS process. The HiPIMS deposited films show a low resistivity down to the order of 10(-4) Omega cm with a good homogeneity across the substrate, making them potential candidates for electrodes in solar cells. The density of electrons reached up to 11 x 10(20) cm(-3), making ionized impurities the main scattering defects. This improvement of the film properties can be related to the specific plasma/target interactions in a HiPIMS discharge. This allows the process to take place in the transition mode and to deposit highly conductive, transparent AZO films on large surfaces at low temperature. While the overall oxygen content is above that of stoichiometric ZnO, higher localization of oxygen is found at the interfaces between crystalline domains with substoichiometric composition. (C) 2016 Elsevier B.V. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE BV, 2016
    Keywords
    Transparent conducting oxide; AZO; Thin films; Electronic properties; HiPIMS
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-132201 (URN)10.1016/j.solmat.2016.07.020 (DOI)000384391700088 ()
    Note

    Funding Agencies|European Commission within the DocMASE project

    Available from: 2016-11-01 Created: 2016-10-21 Last updated: 2017-11-29
    2. Restoring the Properties of Transparent Al-Doped ZnO Thin Film Electrodes Exposed to Ambient Air
    Open this publication in new window or tab >>Restoring the Properties of Transparent Al-Doped ZnO Thin Film Electrodes Exposed to Ambient Air
    Show others...
    2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 27, p. 14426-14433Article in journal (Refereed) Published
    Abstract [en]

    The properties of Al-doped ZnO (AZO) films are known to degrade with exposure to humidity. Different AZO films deposited using reactive direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS) have been aged in ambient laboratory conditions and annealed at temperatures between 160 and 180 degrees C in a N-2 atmosphere. Their electrical and optical properties, which have been investigated both ex situ and in situ during the annealing, are improved. The results of the in situ measurements are interpreted in terms of a diffusion process, where hydroxyl groups are decomposed and water is diffusing out of the films. As hydroxyl groups are known to act as a trap for charge carriers in ZnO, their removal from the film can explain the improvement of the electrical properties by the annealing.

    Place, publisher, year, edition, pages
    AMER CHEMICAL SOC, 2017
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-139560 (URN)10.1021/acs.jpcc.7b03020 (DOI)000405761600006 ()
    Note

    Funding Agencies|European Commission

    Available from: 2017-08-08 Created: 2017-08-08 Last updated: 2017-11-10
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    Deposition of Al-doped ZnO films by high power impulse magnetron sputtering
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  • 174.
    Mickan, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Univ Lorraine, France.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Horwat, David
    Univ Lorraine, France.
    Effect of substrate temperature on the deposition of Al-doped ZnO thin films using high power impulse magnetron sputtering2018In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 347, p. 245-251Article in journal (Refereed)
    Abstract [en]

    Al-doped ZnO thin films were deposited using reactive high power impulse magnetron sputtering at substrate temperatures between room temperature and 600 degrees C. Two sample series with different oxygen partial pressures were studied. The films with the lowest resistivity of 3 x 10(-4) SI cm were deposited at the highest substrate temperature of 600 degrees C. The improvement of the electrical properties could be related to an improvement of the mobility due to the improved crystallinity. This improved crystallinity also increased the stability of the films towards ambient moisture. On the other hand, the detrimental influence of negative oxygen bombardment could be avoided, as the HiPIMS process can take place in the metal or transition mode even at relatively high oxygen partial pressures.

  • 175.
    Mickan, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. University of Lorraine, France.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Rinnert, Herve
    University of Lorraine, France.
    Ghanbaja, Jaafar
    University of Lorraine, France.
    Muller, Dominique
    University of Strasbourg, France.
    Horwat, David
    University of Lorraine, France.
    Room temperature deposition of homogeneous, highly transparent and conductive Al-doped ZnO films by reactive high power impulse magnetron sputtering2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 157, p. 742-749Article in journal (Refereed)
    Abstract [en]

    Aluminum doped zinc oxide (AZO) films have been deposited using reactive high power impulse magnetron sputtering (HiPIMS) and reactive direct current (DC) magnetron sputtering from an alloyed target without thermal assistance. These films have been compared in terms of their optical, electrical and structural properties. While both DC and HiPIMS deposited films show comparable transmittance, their electrical properties are significantly improved by the HiPIMS process. The HiPIMS deposited films show a low resistivity down to the order of 10(-4) Omega cm with a good homogeneity across the substrate, making them potential candidates for electrodes in solar cells. The density of electrons reached up to 11 x 10(20) cm(-3), making ionized impurities the main scattering defects. This improvement of the film properties can be related to the specific plasma/target interactions in a HiPIMS discharge. This allows the process to take place in the transition mode and to deposit highly conductive, transparent AZO films on large surfaces at low temperature. While the overall oxygen content is above that of stoichiometric ZnO, higher localization of oxygen is found at the interfaces between crystalline domains with substoichiometric composition. (C) 2016 Elsevier B.V. All rights reserved.

    Download full text (pdf)
    fulltext
  • 176.
    Mickan, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. University of Lorraine, France.
    Stoffel, Mathieu
    University of Lorraine, France.
    Rinnert, Herve
    University of Lorraine, France.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Horwat, David
    University of Lorraine, France.
    Restoring the Properties of Transparent Al-Doped ZnO Thin Film Electrodes Exposed to Ambient Air2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 27, p. 14426-14433Article in journal (Refereed)
    Abstract [en]

    The properties of Al-doped ZnO (AZO) films are known to degrade with exposure to humidity. Different AZO films deposited using reactive direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS) have been aged in ambient laboratory conditions and annealed at temperatures between 160 and 180 degrees C in a N-2 atmosphere. Their electrical and optical properties, which have been investigated both ex situ and in situ during the annealing, are improved. The results of the in situ measurements are interpreted in terms of a diffusion process, where hydroxyl groups are decomposed and water is diffusing out of the films. As hydroxyl groups are known to act as a trap for charge carriers in ZnO, their removal from the film can explain the improvement of the electrical properties by the annealing.

  • 177.
    Muhammad, Junaid
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lai, W-J
    National Taiwan University.
    Chen, L-C
    National Taiwan University.
    Chen, K-H
    National Taiwan University.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Two-domain formation during the epitaxial growth of GaN (0001) on c-plane Al2O3 (0001) by high power impulse magnetron sputtering2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, no 12, p. 123519-Article in journal (Refereed)
    Abstract [en]

    We study the effect of high power pulses in reactive magnetron sputter epitaxy on the structural properties of GaN (0001) thin films grown directly on Al2O3 (0001) substrates. The epilayers are grown by sputtering from a liquid Ga target, using a high power impulse magnetron sputtering power supply in a mixed N2/Ar discharge. X-ray diffraction, micro-Raman, micro-photoluminescence, and transmission electron microscopy investigations show the formation of two distinct types of domains. One almost fully relaxed domain exhibits superior structural and optical properties as evidenced by rocking curves with a full width at half maximum of 885 arc sec and a low temperature band edge luminescence at 3.47 eV with the full width at half maximum of 10 meV. The other domain exhibits a 14 times higher isotropic strain component, which is due to the higher densities of the point and extended defects, resulting from the ion bombardment during growth. Voids form at the domain boundaries. Mechanisms for the formation of differently strained domains, along with voids during the epitaxial growth of GaN are discussed.

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  • 178.
    Music, Denis
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Chirita, Valeriu
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Kreissig, U.
    Inst. of Ion Beam Phys./Mat. Res., Research Center Rossendorf, P. O. Box 510119, D-01314 Dresden, Germany.
    Czigany, Z.
    Schneider, J.M.
    Materials Chemistry, RWTH-Aachen, D-52056 Aachen, Germany.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Quantum design and synthesis of a boron-oxygen-yttrium phase2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 24, p. 4286-4288Article in journal (Refereed)
    Abstract [en]

    A study was performed on quantum design and synthesis of a boron-oxygen-yttrium (BOY) phase. The calculations predicted that the BOY phase was 0.36 eV/atom more stable than crystalline BO0.17. The results showed that films with Y/B ratios ranging from 0.10 to 0.32, as determined via elastic recoil detection analysis, were grown over wide range of temperatures (300-600°C) and found to withstand 1000°C.

  • 179.
    Music, Denis
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Chirita, Valeriu
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Schneider, Jochen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Effect of chemical composition on the elastic and electrical properties of the boron-oxygen-yttrium system studied by ab initio and experimental means2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 9Article in journal (Refereed)
    Abstract [en]

    The effect of chemical composition on the elastic and electrical properties is studied for the BOxYz system with 0.27less than or equal toxless than or equal to1.14 and 0.36less than or equal tozless than or equal to0.08. We use ab initio calculations to obtain the elastic constants and density of states for BO1.5 and the BOY phase (yttrium substituting for oxygen in the boron suboxide structure). For decreasing x values, the elastic modulus is predicted to increase from 11 to 340 GPa, while electronic structure calculations suggest a shift in electrical properties from insulating to metallic. Thin films in the B-O-Y system are grown by reactive rf magnetron sputtering. As x decreases from 1.14 to 0.27, the elastic modulus increases from 12 to 282 GPa, which is a factor of 24, while resistivity decreases from 7.6+/-0.4 to (3.8+/-0.1)x10(-2) Omegam. The observed shifts in elasticity and resistivity are shown to be induced by the associated changes in chemical bonding from van der Waals type in BO1.5 to icosahedral type in the BOY phase.

  • 180.
    Music, Denis
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Kreissig, U.
    Forschungszentrum Rossendorf e.V., Inst. Ionenstrahlphys./M., PF 510119, D-01314 Dresden, Germany.
    Chirita, Valeriu
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Schneider, J.M.
    Materials Chemistry, RWTH-Aachen, D-52056 Aachen, Germany.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Elastic modulus of amorphous boron suboxide thin films studied by theoretical and experimental methods2003In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, no 2, p. 940-944Article in journal (Refereed)
    Abstract [en]

    Elastic modulus of amorphous boron suboxide thin films was studied by theoretical and experimental methods. It was shown that the increase of x in the a-BOx films from 0.08 to 0.18 decreased the magnitude of the elastic modulus from 273 to 231 GPa. The decrease of the elastic modulus with an increasing amount of O was correlated to the presence of the long B-O bonds with ionic contribution and the reduction of the film density.

  • 181.
    Music, Denis
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Kreissig, U.
    Forschungszentrum Rossendorf e.V., Institute fur IM, PF 510119, 01314 Dresden, Germany.
    Czigany, Zs.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Schneider, Jochen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Elastic modulus-density relationship for amorphous boron suboxide thin films2003In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 76, no 2, p. 269-271Article in journal (Refereed)
    Abstract [en]

    Boron suboxide thin films nave been deposited on Si(100) substrates by reactive RF magnetron sputtering of a sintered B target in an Ar/O2 atmosphere. Elastic recoil detection analysis was applied to determine the film composition and density. Film structure was studied by X-ray diffraction and transmission electron microscopy. The elastic modulus, measured by nanoindentation, was found to decrease as the film density decreased. The relationship was affected by tuning the negative substrate bias potential and the substrate temperature during film growth. A decrease in film density, by a factor of 1.55, caused an elastic modulus reduction by a factor of 4.5, most likely due to formation of nano-pores containing Ar. It appears evident that the large scattering in the published data on elastic properties of films with identical chemical composition can readily be understood by density variations. These results are important for understanding the elastic properties of boron suboxide, but may also be qualitatively relevant for other B-based material systems.

  • 182.
    Music, Denis
    et al.
    Rhein Westfal TH Aachen, Germany.
    Nahif, Farwah
    Rhein Westfal TH Aachen, Germany.
    Sarakinos, Kostas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Friederichsen, Niklas
    Rhein Westfal TH Aachen, Germany.
    M. Schneider, Jochen
    Rhein Westfal TH Aachen, Germany.
    Ab initio molecular dynamics of Al irradiation-induced processes during Al(2)O(3) growth2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 11, p. 111908-Article in journal (Refereed)
    Abstract [en]

    Al bombardment induced structural changes in alpha-Al(2)O(3) (R-3c) and gamma-Al(2)O(3) (Fd-3m) were studied using ab initio molecular dynamics. Diffusion and irradiation damage occur for both polymorphs in the kinetic energy range from 3.5 to 40 eV. However, for gamma-Al(2)O(3)(001) subplantation of impinging Al causes significantly larger irradiation damage and hence larger mobility as compared to alpha-Al(2)O(3). Consequently, fast diffusion along gamma-Al(2)O(3)(001) gives rise to preferential alpha-Al(2)O(3)(0001) growth, which is consistent with published structure evolution experiments.

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  • 183.
    Music, Denis
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Schneider, Jochen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kugler, Veronika Mozhdeh
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Nakao, S.
    National Industrial Research Institute of Nagoya, Nagoya 462-8510, Japan.
    Jin, P.
    National Industrial Research Institute of Nagoya, Nagoya 462-8510, Japan.
    Östblom, Mattias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Synthesis and mechanical properties of boron suboxide thin films2002In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 20, no 2, p. 335-337Article in journal (Refereed)
    Abstract [en]

    The synthesis and mechanical properties of boron suboxide thin films deposited on silicon and graphite substrates was discussed. The deposition was performed using reactive magnetron sputtering technique, and amorphous films were obtained. The affect of varying O2 partial pressure on film composition and microstructure was studied using spectroscopic techniques. It was found that variation of partial pressure from 0.02 to 0.21 resulted in a decrease in elastic modulus from 272 to 109 GPa.

  • 184.
    Nadhom, Hama
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Rouf, Polla
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Chemical vapor deposition of metallic films using plasma electrons as reducing agents2020In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 38, no 3, article id 033402Article in journal (Refereed)
    Abstract [en]

    Metallic thin films are key components in electronic devices and catalytic applications. Deposition of a conformal metallic thin film requires using volatile precursor molecules in a chemical vapor deposition (CVD) process. The metal centers in such molecules typically have a positive valence, meaning that reduction of the metal centers is required on the film surface. Powerful molecular reducing agents for electropositive metals are scarce and hamper the exploration of CVD of electropositive metals. The authors present a new CVD method for depositing metallic films where free electrons in a plasma discharge are utilized to reduce the metal centers of chemisorbed precursor molecules. They demonstrate this method by depositing Fe, Co, and Ni from their corresponding metallocenes using electrons from an argon plasma as a reducing agent.

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  • 185.
    Nakagomia, Shinji
    et al.
    Ishinomaki Senshu University.
    Wingqvist, Gunilla
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Åbom, Elisabeth
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Hydrogen sensing by NKN thin film with high dielectric constant and ferroelectric property2005In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 108, p. 490-495Article in journal (Refereed)
    Abstract [en]

    Hydrogen sensing properties of sodium potassium niobate NaxKyNbOz (NKN) thin films were studied. The NKN thin films were prepared by reactive rf magnetron sputtering. NKN is a ferroelectric material with high dielectric constant. The polarization increases in hydrogen ambient and decreases in oxygen ambient. The conductivity of the NKN film in hydrogen ambient is higher than in oxygen ambient, and these changes are reversible. The threshold voltage of the current-voltage (I-V) characteristics depends on the hydrogen concentration, and a large response of 3.3V was obtained.

  • 186.
    Nakao, S.
    et al.
    National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Moriyama, Nagoya 463-8560, Japan.
    Jin, P.
    National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Moriyama, Nagoya 463-8560, Japan.
    Music, Denis
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Ikeyama, M.
    National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Moriyama, Nagoya 463-8560, Japan.
    Miyagawa, Y.
    National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Moriyama, Nagoya 463-8560, Japan.
    Miyagawa, S.
    National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Moriyama, Nagoya 463-8560, Japan.
    Influence of high-energy Si+ ion irradiation on microstructure and mechanical properties of alumina films2002In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 158-159, p. 534-537Article in journal (Refereed)
    Abstract [en]

    Amorphous alumina films, approximately 600 nm in thickness, prepared on Si(100) substrates by RF magnetron sputtering were irradiated with 2.0 MeV Si ions at a dose of 1 × 1017 ions/cm2 and the influence on the composition, microstructure, and mechanical properties was examined by Rutherford backscattering. X-ray diffraction and nano-indentation measurements. It was found that the O/Al ratio in the films was approximately 1.5, and there was no significant alteration in this ratio after ion irradiation. However, a structural change from amorphous to the crystalline ?-alumina was observed. Hardness and elastic modulus of the irradiated film were significantly increased from approximately 11 and 181 GPa up to approximately 25 and 246 GPa, respectively. © 2002 Elsevier Science B.V. All rights reserved.

  • 187.
    Ni, Wei-Xin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Lyutovich, K.
    Institut fuer Halbleitertechnik, Universität Stuttgart, 70569 Stuttgart, Germany.
    Alami, Jones
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Tengstedt, Carl
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Bauer, M.
    Institut fuer Halbleitertechnik, Universität Stuttgart, 70569 Stuttgart, Germany.
    Kasper, E.
    Institut fuer Halbleitertechnik, Universität Stuttgart, 70569 Stuttgart, Germany.
    X-ray reciprocal space mapping studies of strain relaxation in thin SiGe layers (=100 nm) using a low temperature growth step2001In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 227-228, p. 756-760Conference paper (Other academic)
    Abstract [en]

    Relaxation of thin SiGe layers (~90 nm) grown by molecular beam epitaxy using a low temperature growth step (120-200°C) has been investigated using two-dimensional reciprocal space mapping of X-ray diffraction. The samples studied have been divided in two groups, depending on the substrate cooling process during the growth of the low temperature layer. It has been found that a higher degree of relaxation was easily achieved for the sample group without growth interruption. A process window for full relaxation of the Si0.74Ge0.26 layer has been observed in the range of 140-150°C. © 2001 Elsevier Science B.V.

  • 188.
    Nunez, Julius Andrew P.
    et al.
    Univ Philippines Manila, Philippines; Univ Philippines Diliman, Philippines.
    Salapare, Hernando S. III
    Univ Philippines Manila, Philippines; Univ Philippines Open Univ, Philippines; Pamantasan Ng Lungsod Ng Maynila, Philippines.
    Villamayor, Michelle M
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    De Los Santos Valladares, Luis
    Univ Cambridge, England; Univ Nacl Mayor San Marcos, Peru.
    Ramos, Henry J.
    Univ Philippines Diliman, Philippines.
    Photodegradation of Rhodamine 6G by Amorphous TiO2 Films Grown on Polymethylmethacrylate by Magnetron Sputtering2017In: PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES, ISSN 2070-2051, Vol. 53, no 6, p. 1022-1027Article in journal (Refereed)
    Abstract [en]

    Titanium dioxide (TiO2) was deposited on polymethylmethacrylate (PMMA) substrates by magnetron sputtering using a Compact Planar Magnetron sputtering device at different flow rate ratios of O-2/Ar. The deposited TiO2 on PMMA substrates were characterized using X-ray Diffraction analysis, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, UV-Visible Spectroscopy, and Scanning Electron Microscopy (SEM). These techniques confirm the deposition of a chemically stable amorphous TiO2 layer on the PMMA surface. Photocatalytic activity of the amorphous TiO2 layers were tested via photodegradation of Rhodamine 6G (Rh6G) dye solution. The samples were able to degrade 18-27% of the Rh6G solution after the initial 25 minutes of UV irradiation and complete degradation of Rh6G was observed after 7 hours of UV irradiation.

  • 189.
    Nyberg, T.
    et al.
    Uppsala universitet.
    Berg, S.
    Uppsala universitet.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Hartig, K.
    Cardinal CG, Wisconsin, USA.
    Eliminating the hysteresis effect for reactive sputtering processes2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 16, p. 164106-Article in journal (Refereed)
    Abstract [en]

    Reactive sputter processes frequently exhibit stability problems. The cause of this is that these processes normally exhibit hysteresis effects in the processing curves. Eliminating the hysteresis would significantly simplify the use of reactive sputtering processes. So far the only known way of eliminating the hysteresis is to increase the pumping speed to unrealistically high values. By an increased understanding of the process we have realized a fully realistic technique to eliminate the hysteresis for reactive sputtering processes. By simply reducing the size of the target sputter erosion zone below a critical value, simulations predicted that hysteresis should be eliminated. This has been experimentally verified for reactive sputtering of Al in an Ar O2 atmosphere. The fundamental explanation to this behavior as well as the experimental verification are presented.

  • 190.
    Pedersen, Henrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Larsson, Petter
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Aijaz, Asim
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    A novel high-power pulse PECVD method2012In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 22, p. 4562-4566Article in journal (Refereed)
    Abstract [en]

    A novel plasma enhanced CVD (PECVD) technique has been developed in order to combine energetic particle bombardment and high plasma densities found in ionized PVD with the advantages from PECVD such as a high deposition rate and the capability to coat complex and porous surfaces. In this PECVD method, an ionized plasma is generated above the substrate by means of a hollow cathode discharge. The hollow cathode is known to generate a highly ionized plasma and the discharge can be sustained in direct current (DC) mode, or in high-power pulsed (HiPP) mode using short pulses of a few tens of microsecond. The latter option is similar to the power scheme used in high power impulse magnetron sputtering (HiPIMS), which is known to generate a high degree of ionization of the sputtered material, and thus providing new and added means for the synthesis of tailor-made thin films. In this work amorphous carbon coatings containing copper, have been deposited using both HiPP and DC operating conditions. Investigations of the bulk plasma using optical emission spectroscopy verify the presence of Ar+, C+ as well as Cu+ when running in pulsed mode. Deposition rates in the range 30 mu m/h have been obtained and the amorphous, copper containing carbon films have a low hydrogen content of 4- 5 at%. Furthermore, the results presented here suggest that a more efficient PECVD process is obtained by using a superposition of HiPP and DC mode, compared to using only DC mode at the same average input power.

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  • 191.
    Pilch, Iris
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Caillault, L.
    University of Paris 11, France.
    Minea, T.
    University of Paris 11, France.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Tal, Alexey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. National University of Science and Technology MISIS, Russia.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. National University of Science and Technology MISIS, Russia.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Brenning, Nils
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. KTH Royal Institute Technology, Sweden.
    Nanoparticle growth by collection of ions: orbital motion limited theory and collision-enhanced collection2016In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 39, p. 395208-Article in journal (Refereed)
    Abstract [en]

    The growth of nanoparticles in plasma is modeled for situations where the growth is mainly due to the collection of ions of the growth material. The model is based on the classical orbit motion limited (OML) theory with the addition of a collision-enhanced collection (CEC) of ions. The limits for this type of model are assessed with respect to three processes that are not included: evaporation of the growth material, electron field emission, and thermionic emission of electrons. It is found that both evaporation and thermionic emission can be disregarded below a temperature that depends on the nanoparticle material and on the plasma parameters; for copper in our high-density plasma this limit is about 1200 K. Electron field emission can be disregarded above a critical nanoparticle radius, in our case around 1.4 nm. The model is benchmarked, with good agreement, to the growth of copper nanoparticles from a radius of 5 nm-20 nm in a pulsed power hollow cathode discharge. Ion collection by collisions contributes with approximately 10% of the total current to particle growth, in spite of the fact that the collision mean free path is four orders of magnitude longer than the nanoparticle radius.

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  • 192.
    Pilch, Iris
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Söderström, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Brenning, N
    Royal Institute Technology, Sweden .
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Size-controlled growth of nanoparticles in a highly ionized pulsed plasma2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 3Article in journal (Refereed)
    Abstract [en]

    Copper nanoparticles (NPs) were synthesized using a high power pulsed hollow cathode technique and the produced NPs were studied as a function of pulse parameters, i.e., frequency, peak current, and pulse width. It was found that the particle size can be altered in a range from 10 to 40 nm by changing any one of the pulse parameters. The mechanisms of NP synthesis with respect to a pulsed discharge and a high degree of ionization of the sputtered material are discussed.

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  • 193.
    Pilch, Iris
    et al.
    Linköping University, Department o