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  • 51.
    Palisaitis, Justinas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Persson, Ingemar
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Halim, Joseph
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Persson, Per O. Å.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    On the Structural Stability of MXene and the Role of Transition Metal Adatoms2018Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, nr 23, s. 10850-10855Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present communication, the atomic structure and coordination of surface adsorbed species on Nb2C MXene is investigated over time. In particular, the influence of the Nb adatoms on the structural stability and oxidation behavior of the MXene is addressed. This investigation is based on plan-view geometry observations of single Nb2C MXene sheets by a combination of atomic-resolution scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and STEM image simulations.

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  • 52.
    Persson, Per
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    McKenzie, D R
    University of Sydney.
    Bilek, M M M
    University of Sydney.
    Formation of the MAX-phase oxycarbide Ti2AlC1-xOx studied via electron energy-loss spectroscopy and first-principles calculations2009Ingår i: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 80, nr 9, s. 092102-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oxygen incorporation in the Ti2AlC MAX phase and TiC was investigated in the electron microscope using spatially resolved fine-structure electron energy-loss spectroscopy analysis. Corresponding fine structures were calculated within the full-potential-linearized augmented plane-wave framework. In the calculations, oxygen was substituted for aluminum and carbon in Ti2AlC as well as for carbon in TiC, in concentrations of 3.1, 6.2, and 12.5 at %. Comparison of calculated and measured spectra shows that oxygen is incorporated on the carbon site in both TiC and Ti2AlC. These findings reveal the existence of MAX phase oxycarbide MA(O,C) alloys and O as a third X element in addition to C and N.

  • 53.
    Persson, P.O.A.
    et al.
    Persson, P.O.Å., School of Physics, University of Sydney, NSW 2006, Australia.
    Rosen, Johanna
    School of Physics, University of Sydney, NSW 2006, Australia.
    McKenzie, D.R.
    School of Physics, University of Sydney, NSW 2006, Australia.
    Bilek, M.M.M.
    School of Physics, University of Sydney, NSW 2006, Australia.
    Höglund, Carina
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    A solid phase reaction between Ti Cx thin films and Al2 O3 substrates2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ti Cx thin films were deposited on Al2 O3 substrates at 900 °C by using a multiple cathode high current pulsed cathodic arc. The Ti:C pulse ratio and, hence, the composition was varied from C rich to Ti rich. It is found that the Al2 O3 substrate is decomposed and reacts with the Ti Cx film to incorporate significant amounts of O and Al in the growing film. When the stoichiometry is suitable, epitaxially oriented Ti2 AlC MAX phase with significant O incorporated is formed. The results indicate that Al2 O3 is not an ideal substrate material for the growth of transition metal carbides and MAX phase thin films. © 2008 American Institute of Physics.

  • 54.
    Petruhins, Andrejs
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ingason, Arni Sigurdur
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Mockuté, Aurelija
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Junaid, Muhammad
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Birch, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Lu, Jun
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Persson, Per O A
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Phase stability of Crn+1GaCn MAX phases from first principles and Cr2GaC thin-film synthesis using magnetron sputtering from elemental targets2013Ingår i: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 7, nr 11, s. 971-974Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ab-initio calculations have been used to investigate the phase stability and magnetic state of Crn+ 1GaCn MAX phase. Cr2GaC (n = 1) was predicted to be stable, with a ground state corresponding to an antiferromagnetic spin configuration. Thin-film synthesis by magnetron sputtering from elemental targets, including liquid Ga, shows the formation of Cr2GaC, previously only attained from bulk synthesis methods. The films were deposited at 650 degrees C on MgO(111) substrates. X-ray diffraction and high-resolution transmission electron microscopy show epitaxial growth of (000) MAX phase.

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  • 55.
    Petruhins, Andrejs
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ingason, Arni Sigurdur
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Lu, Jun
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Magnus, Fridrik
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Olafsson, Sveinn
    Science Institute, University of Iceland, Reykjavik, Iceland.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Synthesis and characterization of magnetic (Cr0.5Mn0.5)2GaC thin films2015Ingår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, nr 13, s. 4495-4502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Growth of (Cr0.5Mn0.5)2GaC thin films from C, Ga, and compound Cr0.5Mn0.5 targets is reported for depositions on MgO (111), 4H-SiC (0001), and Al2O3 (0001) with and without a NbN (111) seed layer. Structural quality is found to be highly dependent on the choice of substrate with MgO (111) giving the best results as confirmed by X-ray diffraction and transmission electron microscopy. Phase pure, high crystal quality MAX phase thin films are realized, with a Cr:Mn ratio of 1:1. Vibrating sample magnetometry shows a ferromagnetic component from 30 K up to 300 K, with a measured net magnetic moment of 0.67 μB per metal (Cr + Mn) atom at 30 K and 5 T. The temperature dependence of the magnetic response suggests competing magnetic interactions with a resulting non-collinear magnetic ordering.

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  • 56.
    Rosen, Johanna
    et al.
    Rhein Westfal TH Aachen.
    Anders, A
    Lawrence Berkeley Laboratory.
    Time and material dependence of the voltage noise generated by cathodic vacuum arcs2005Ingår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 38, nr 23, s. 4184-4190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The high frequency fluctuations of the burning voltage of cathodic vacuum arcs have been investigated in order to extract information on cathode processes, especially concerning evolution in time after arc ignition. Eight cathode materials (W, Ta, Hf, Ti, Ni, An, Sn, Bi) were selected covering a wide range of cohesive energy. The voltage noise was recorded using both a broad-band voltage divider and an attenuator connected to a fast oscilloscope (limits 1 GHz analog and 5 GS s(-1) digital). Fast Fourier transform revealed a power spectrum that is linear in log-log presentation, with a slope of 1/f(2), where f is the frequency (brown noise). The amplitude of the spectral power of the voltage noise was found to scale with the cohesive energy, in agreement with earlier measurements at lower resolution. These basic results do not depend on the time after arc initiation. However, lower arc current in the beginning of the pulse shows greater voltage noise, suggesting an inverse relation between the noise amplitude and number of emission sites (cathode spot fragments).

  • 57.
    Rosen, Johanna
    et al.
    Rhein Westfal TH Aachen.
    Anders, A
    Lawrence Berkeley National Laboratory.
    Mraz, S
    Rhein Westfal TH Aachen.
    Atiser, A
    Rhein Westfal TH Aachen.
    Schneider, JM
    Rhein Westfal TH Aachen.
    Influence of argon and oxygen on charge-state-resolved ion energy distributions of filtered aluminum arcs2006Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, nr 12, s. 123303-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The charge-state-resolved ion energy distributions (IEDs) in filtered aluminum vacuum arc plasmas were measured and analyzed at different oxygen and argon pressures in the range of 0.5-8.0 mTorr. A significant reduction of the ion energy was detected as the pressure was increased, most pronounced in an argon environment and for the higher charge states. The corresponding average charge state decreased from 1.87 to 1.0 with increasing pressure. The IEDs of all metal ions in oxygen were fitted with shifted Maxwellian distributions. The results show that it is possible to obtain a plasma composition with a narrow charge-state distribution as well as a narrow IED. These data may enable tailoring thin film properties through selecting growth conditions that are characterized by predefined charge state and energy distributions.

  • 58.
    Rosen, Johanna
    et al.
    RWTH, Aachen, Germany.
    Anders, A
    Lawrence Berkeley Laboratory.
    Mraz, S
    RWTH, Aachen, Germany.
    Schneider, JM
    RWTH, Aachen, Germany.
    Charge-state-resolved ion energy distributions of aluminum vacuum arcs in the absence and presence of a magnetic field2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 97, nr 10, s. 103306-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The charge-state-resolved ion energy distributions (IEDs) of aluminum vacuum are plasma species were measured and analyzed for different geometric and magnetic field configurations. The IEDs were fitted by shifted Maxwellian distributions. Plasma expansion in the absence of a magnetic field showed higher ion energies for higher charge states. The introduction of a magnetic field (independent of geometric configuration) resulted in a broader distribution and increased average ion energies. The energy gain was approximately proportional to the charge state, which may be due to the presence of electric fields in the magnetized plasma. The evolution of ion energy distributions is relevant to thin-film growth, and it is shown that the IEDs can be modified by suitable magnetic field configurations.

  • 59.
    Rosen, Johanna
    et al.
    Rhein Westfal TH Aachen.
    Larsson, K
    University of Uppsala.
    Schneider, JM
    Rhein Westfal TH Aachen.
    Ab initio molecular dynamics study of hydrogen removal by ion-surface interactions2005Ingår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 17, nr 15, s. L137-L142Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The energy dependence of surface reactions has been investigated through ab initio MD simulations for collisions between Al1+ and a gibbsite surface. No change in surface composition was observed for 0 eV initial kinetic energy of Al1+. An increase in energy to 3.5 eV resulted in extended surface migration of hydrogen, subsequent H-2 formation and desorption from the surface. These results may be understood based on thermodynamics and an increase in entropy upon H-2 formation. They are of fundamental importance for an increased understanding of thin film growth through the correlation between ion energy and film composition. They may also indicate a pathway to affect impurity incorporation during film growth.

  • 60.
    Rosen, Johanna
    et al.
    Rhein Westfal TH Aachen.
    Mraz, S
    Rhein Westfal TH Aachen.
    Kreissig, U
    Rhein Westfal TH Aachen.
    Music, D
    Rhein Westfal TH Aachen.
    Schneider, J
    Rhein Westfal TH Aachen.
    Effect of ion energy on structure and composition of cathodic arc deposited alumina thin films2005Ingår i: Plasma chemistry and plasma processing, ISSN 0272-4324, E-ISSN 1572-8986, Vol. 25, nr 4, s. 303-317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of energy supplied to the growing alumina film on the composition and structure has been investigated by varying substrate temperature and substrate bias potential. The constitution and composition were studied by X-ray diffraction and elastic recoil detection analysis, respectively. Increasing the substrate bias potential from -50 to -100 V caused the amorphous or weakly crystalline films to evolve into stoichiometric, crystalline films with a mixture of the alpha- and gamma-phase above 700 degrees C, and. gamma-phase dominated films at temperatures as low as 200 degrees C. All films had a grain size of less than 10 nm. The combined constitution and grain size data is consistent with previous work stating that. - alumina is thermodynamically stable at grain sizes less than 12 nm [McHale et al., Science 277, 788 ( 1997)]. In order to correlate phase formation with synthesis conditions, the plasma chemistry and ion energy distributions were measured at synthesis conditions. These results indicate that for a substrate bias potential of - 50V, ion energies in excess of 100 eV are attained, both from a high energy tail and the accelerated ions with charge greater than 1. These results are of importance for an increased understanding of the evolution of film composition and microstructure, also providing a pathway to. - alumina growth at temperatures as low as 200 degrees C.

  • 61.
    Rosen, Johanna
    et al.
    University of Sydney.
    Persson, P. O. A.
    University of Sydney.
    Ionescu, M.
    University of Sydney.
    Pigott, J.
    University of Sydney.
    McKenzie, D. R.
    University of Sydney.
    Bilek, M. M. M.
    University of Sydney.
    Influence of gas entry point on plasma chemistry, ion energy and deposited alumina thin films in filtered cathodic arc2007Ingår i: Plasma chemistry and plasma processing, ISSN 0272-4324, E-ISSN 1572-8986, Vol. 27, nr 5, s. 599-608Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of gas entry point on the plasma chemistry, ion energy distributions and resulting alumina thin film growth have been investigated for a d.c. cathodic arc with an aluminum cathode operated in an oxygen/argon atmosphere. Ions of aluminum, oxygen and argon, as well as ions originating from the residual gas are investigated, and measurements for gas entry at both the cathode and close to the substrate are compared. The latter was shown to result in higher ion flux, lower levels of ionised residual gas, and lower ion energies, as compared to gas inlet at the cathode. These plasma conditions that apply when gas entry at the substrate is used result in a higher film deposition rate, less residual gas incorporation, and more stoichiometric alumina films. The results show that the choice of gas entry point is a crucial parameter in thin film growth using reactive PVD processes such as reactive cathodic arc deposition.

  • 62.
    Rosen, Johanna
    et al.
    University of Sydney.
    Persson, P.O.A.
    University of Sydney.
    Ionescu, M.
    Australian Nuclear Science and Technology Organization.
    Kondyurin, A.
    University of Sydney.
    McKenzie, D.R.
    University of Sydney.
    Bilek, M.M.M.
    University of Sydney.
    Oxygen incorporation in Ti2AlC thin films2008Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, nr 6, s. 064102-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin films of Ti2AlC MAX phase have been deposited using a multiple cathode pulsed cathodic arc. Evidence for substantial oxygen incorporation in the MAX phase is presented, likely originating from residual gas present in the vacuum chamber during deposition. The characteristic MAX phase crystal structure is maintained, in agreement with ab initio calculations, supporting substitutional O in C lattice positions. On the basis of these results, we propose the existence of a MAX phase-like material with material properties tuned by the incorporation of oxygen. Additionally, possible unintentional O incorporation in previously reported MAX phase materials is suggested.

  • 63.
    Rosen, Johanna
    et al.
    University of Sydney.
    Ryves, L.
    University of Sydney.
    Persson, P. O. A.
    University of Sydney.
    Bilek, M. M. M.
    University of Sydney.
    Deposition of epitaxial Ti2AlC thin films by pulsed cathodic arc2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 5, s. 056101-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A multicathode high current pulsed cathodic arc has been used to deposit Ti2AlC thin films belonging to the group of nanolaminate ternary compounds of composition M(n+1)AX(n). The required stoichiometry was achieved by means of alternating plasma pulses from three independent cathodes. We present x-ray diffraction and transmission electron microscopy analysis showing that epitaxial single phase growth of Ti2AlC has been achieved at a substrate temperature of 900 degrees C. Our results demonstrate a powerful method for MAX phase synthesis, allowing for phase tuning within the M(n+1)AX(n) system.

  • 64.
    Rosen, Johanna
    et al.
    Rhein Westfal TH Aachen.
    Schneider, JA
    Rhein Westfal TH Aachen.
    Larsson, K
    Uppsala University.
    Ab initio studies of adsorption and migration surface processes on an alpha-Al2O3 surface2005Ingår i: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 135, nr 01-Feb, s. 90-94Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface processes on alpha-Al2O3 (0001) have been investigated theoretically using density functional theory. Ion-surface interactions prior to collision were investigated by means of ab initio molecular dynamics simulations, showing an adsorbate trajectory towards a preferred adsorption site. Furthermore, the adsorption process at different surface sites was investigated, together with calculations of barriers for migration between these sites. Although the equilibrium (bulk) adsorption site was energetically favourable, the presence and magnitude of the migration barriers indicate that activation energy is necessary to form the equilibrium surface structure. These results are of importance for a fundamental understanding of ion-surface interactions.

  • 65.
    Rosen, Johanna
    et al.
    Rhein Westfal TH Aachen.
    Schneider, JM
    Rhein Westfal TH Aachen.
    Larsson, K
    Uppsala University.
    Ab initio molecular dynamics study of ion-surface interactions2005Ingår i: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 134, nr 5, s. 333-336Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ion-surface collisions have been investigated theoretically using ab initio molecular dynamics within density functional theory. The temporal evolution of the position of the bombarding ion, as well as its nearest neighbors, was studied for initial kinetic energies of 0 and 3.5 eV (0 and 5 km/s, respectively). Also investigated was the ion-surface interaction prior to collision and the following energy transfer, as indicated by changes in ion velocity. At 3.5 eV collision energy, the calculation results suggest the formation of local structural disorder within the simulation time frame studied. These results are of fundamental importance for an increased understanding of the ion-surface interaction during a collision event, with resulting changes in atomic level structure.

  • 66.
    Rosen, Johanna
    et al.
    Rhein Westfal TH Aachen.
    Schneider, JM
    Rhein Westfal TH Aachen.
    Larsson, K
    Uppsala University.
    Thin film growth related adsorption study of Al and O ions on an alpha-Al2O3 surface2004Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, nr 50, s. 19320-19324Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The surface reactivity of alpha-Al2O3 (0001) has been investigated theoretically using density functional theory. The adsorption process of Al+, Al2+, Al3+, and O+ were studied to identify possible preferential adsorption sites during thin film growth. Differences in near surface atomic displacements (e.g., adsorption-induced surface reconstructions), energies, and bonding character have been evaluated. The adsorption energies for the metallic ions showed a strong dependence on both initial charge and adsorption site. The O+ ions showed no site dependence, but adsorption energies similar to those calculated for Al+. The results indicate that the adsorption of O+ and Al3+ may favor the formation of an amorphous structure, which is consistent with experimental observations. The results are of fundamental importance for the understanding of thin film microstructure evolution.

  • 67.
    Rosen, Johanna
    et al.
    University of Sydney.
    Schneider, Jochen M.
    University of Sydney.
    Anders, Andre
    University of Sydney.
    Charge state dependence of cathodic vacuum arc ion energy and velocity distributions2006Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, nr 14, s. 141502-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the literature, conflicting conclusions are reported concerning the charge state dependence of cathodic arc ion energy and velocity distributions. It appears that data from electrostatic energy analyzers indicate charge state dependence of ion energy, whereas time-of-flight methods support charge state independence of ion velocity. Here the authors present charge-state-resolved ion energy distributions and calculate the corresponding ion velocity distributions in aluminum vacuum arc plasma. They show that the conflicting conclusions reported in the literature for the two different characterization techniques may originate from the commonly employed data interpretation of energy and velocity, in which peak values and average values are not carefully distinguished.

  • 68.
    Rosen, Johanna
    et al.
    University of Sydney.
    Warschkow, O.
    University of Sydney.
    McKenzie, D. R.
    University of Sydney.
    Bilek, M. M. M.
    University of Sydney.
    Amorphous and crystalline phases in thermal quench simulations of alumina2007Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 126, nr 20, s. 204709-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The authors report molecular dynamics simulations of alumina (Al2O3) during crystallization from the melt. Using liquid quench methods, they investigate the effect of cooling rate on the structural evolution of the alpha, kappa, and the bixbyite phases. A critical temperature window is identified, where the time spent in this window is crucial in determining the extent to which the systems approach crystallinity. A strong dependence is observed between the final structure and the quench rate, which is most pronounced for the alpha phase and to lesser extent for the other phases. The results show that the different phases have different tendencies to crystallize that are determined by energetics, complexity of crystal structure, and the number of metastable states.

  • 69.
    Rosen, Johanna
    et al.
    Rhein Westfal TH Aachen.
    Widenkvist, E
    Uppsala University.
    Larsson, K
    Uppsala University.
    Kreissig, U
    Research Center Rossendorf.
    Mraz, S
    Rhein Westfal TH Aachen.
    Martinez, C
    Rhein Westfal TH Aachen.
    Music, D
    Rhein Westfal TH Aachen.
    Schneider, JM
    Rhein Westfal TH Aachen.
    Reducing the impurity incorporation from residual gas by ion bombardment during high vacuum magnetron sputtering2006Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, nr 19, s. 191905-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of ion energy on the hydrogen incorporation has been investigated for alumina thin films, deposited by reactive magnetron sputtering in an Ar/O-2/H2O environment. Ar+ with an average kinetic energy of similar to 5 eV was determined to be the dominating species in the plasma. The films were analyzed with x-ray diffraction, x-ray photoelectron spectroscopy, and elastic recoil detection analysis, demonstrating evidence for amorphous films with stoichiometric O/Al ratio. As the substrate bias potential was increased from -15 V (floating potential) to -100 V, the hydrogen content decreased by similar to 70%, from 9.1 to 2.8 at. %. Based on ab initio calculations, these results may be understood by thermodynamic principles, where a supply of energy enables surface diffusion, H-2 formation, and desorption [Rosen , J. Phys.: Condens. Matter 17, L137 (2005)]. These findings are of importance for the understanding of the correlation between ion energy and film composition and also show a pathway to reduce impurity incorporation during film growth in a high vacuum ambient.

  • 70.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Characterization of metal plasma streams from arc discharges in a reactive environment2002Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Alumina is a material used in many applications mainly due to its chemical inertness and wear resistance at high temperatures. Despite this, the understanding of alumina thin films is not satisfactory, as can be concluded from the diverging material properties reported in the literature. The objective of this study is to contribute towards a fundamental understanding of the correlation between synthesis conditions, thin film composition and microstructure. A detailed description of the plasma chemistry including ion charge states is essential to achieve this task. The growth technique under investigation is pulsed cathodic arc, and cathodic arc plasma under varying process conditions have been characterized.

    The temporal development of the plasma chemistry has been investigated. Pulse-to­ pulse fluctuations of the plasma chemistry in the presence of magnetic fields, for an aluminium arc in an oxygen environment, were found to increase as the magnetic field strength increased. These results are explained by a varying energy input during plasma production, as seen through a measured fluctuating cathode potential.

    Further investigations dealt with temporal development of the plasma chemistry and average charge state within the pulse, for a zirconium and chromium arc in a nitrogen environment. A large non-metal fraction was observed in the beginning of the plasma pulse, which can be explained by the formation and erosion of a compound layer at the cathode surface. As the pressure increased, the concentration of these ions was found to increase, both in amplitude as well as in width out in the pulse. The average charge state also showed a time and pressure dependence, the former most pronounced at lower pressures with higher charge state in the beginning of the pulse. With increasing pressure, the charge state decreased towards a steady state value, which is proposed to be due to a higher probability of collisions in the plasma with possible charge exchanges.

  • 71.
    Rosén, Johanna
    et al.
    Materials Chemistry, RWTH-Aachen.
    Anders, A.
    Lawrence Berkeley National Laboratory, California.
    Hultman, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Schneider, J.M.
    Materials Chemistry, RWTH-Aachen.
    Charge state and time resolved plasma composition of a pulsed zirconium arc in a nitrogen environment2004Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 96, nr 9, s. 4793-4799Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The species and ion charge state evolution of a pulsed cathodic arc plasma was investigated at different pressures. A zirconium cathode was operated in a nitrogen environment, and the plasma composition was analyzed by time-of-flight charge-to-mass spectrometry. Large plasma chemistry changes were detected with respect to time and pressure, The 250 µs plasma pulse can be divided in two characteristic phases: a transient phase before 150 µs and a steady state phase for all later times. The measured changes in plasma chemistry in the transient phase at p~10-5 Torr are explained by charge transfer collisions, while the increasing N+ fraction in the p > 10 -5 Torr range most likely originates from erosion of the nitrided cathode surface. In the steady-state phase, a pressure-induced change from higher to lower charge states was observed, which was mainly due to scattering of self-sputtered metal followed by metal ion-atom charge exchange collisions. These results are of importance for understanding the evolution of thin film composition and microstructure during reactive plasma deposition. © 2004 American Institute of Physics.

  • 72.
    Rosén, Johanna
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Anders, A.
    Lawrence Berkeley Natl. Laboratory, Berkeley, CA 94720, United States.
    Hultman, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Schneider, J.M.
    Materials Chemistry, RWTH-Aachen, D-52056 Aachen, Germany.
    Temporal development of the composition of Zr and Cr cathodic arc plasma streams in a N2 environment2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 94, nr 3, s. 1414-1419Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development of the plasma composition in a pulsed plasma stream generated by cathodic arc was described. The time-resolved plasma composition for the cathode materials was analyzed by using time-of-flight charge-to-mass spectrometry. The results showed that the average charge state was affected by the reactive gas pressure and also by the time after ignition.

  • 73.
    Rosén, Johanna
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Anders, A.
    Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States.
    Schneider, J.M.
    Materials Chemistry, RWTH-Aachen, D-52056 Aachen, Germany.
    Plasma chemistry fluctuations in a reactive arc plasma in the presence of magnetic fields2002Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 80, nr 22, s. 4109-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    [No abstract available]

  • 74.
    Rosén, Johanna
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Simak, Sergey
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    McKenzie, D R
    University of Sydney.
    Bilek, M M M
    University of Sydney.
    Oxygen incorporation in Ti2AlC: Tuning of anisotropic conductivity2010Ingår i: APPLIED PHYSICS LETTERS, ISSN 0003-6951, Vol. 97, nr 7, s. 073103-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The substitution of oxygen for carbon in Ti2AlC M((n+1))AX(n) (MAX) phase, forming Ti2AlC1-xOx, has recently been reported. In this paper we simulate the effect of oxygen incorporation on mechanical and electronic properties using ab initio calculations. While the mechanical properties are not sensitive to the change in composition, the electronic properties can be tuned by varying the oxygen concentration. As the concentration increases, the conduction changes from in plane, typical of MAX phases, to conduction also in the c-direction. The conduction along c passes from insulating to n-type and then finally to p-type. These findings reveal an anisotropic semiconducting material.

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  • 75.
    Rosén, Johanna
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Warschkow, O
    University of Sydney.
    Electronic structure of amorphous indium oxide transparent conductors2009Ingår i: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 80, nr 11, s. 115215-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using empirical atomistic simulations and density functional theory (DFT), we examine the atomic and electronic structure of pure-and tin-doped indium oxide in various degrees of amorphisation. Atomic structures ranging from maximally amorphous (within fixed periodic boundary conditions) to fully crystalline are prepared using liquid-quench molecular dynamics simulations in which the cooling/quench rate is the governing parameter. The final structures are reoptimized using DFT and the electronic structure (band gaps and carrier effective masses) are compared to the crystalline material. We find that the conduction bands of In2O3 are quite resilient in several aspects to changes in the atomic structure. This suggests that local coordination geometries around indium and oxygen are less critical to transparent conductivity than previously thought.

  • 76.
    Salikhov, Ruslan
    et al.
    University of Duisburg Essen, Germany.
    Semisalova, Anna S.
    University of Duisburg Essen, Germany; Moscow MV Lomonosov State University, Russia; Helmholtz Zentrum Dresden Rossendorf, Germany.
    Petruhins, Andrejs
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Ingason, Arni Sigurdur
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Wiedwald, Ulf
    University of Duisburg Essen, Germany.
    Farle, Michael
    University of Duisburg Essen, Germany.
    Magnetic Anisotropy in the (Cr0.5Mn0.5)(2)GaC MAX Phase2015Ingår i: MATERIALS RESEARCH LETTERS, ISSN 2166-3831, Vol. 3, nr 3, s. 156-160Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetic MAX phase (Cr0.5Mn0.5)(2)GaC thin films grown epitaxially on MgO(111) substrates were studied by ferromagnetic resonance at temperatures between 110 and 300 K. The spectroscopic splitting factor g = 2.00 +/- 0.01 measured at all temperatures indicates pure spin magnetism in the sample. At all temperatures we find the magnetocrystalline anisotropy energy to be negligible which is in agreement with the identified pure spin magnetism.

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  • 77.
    Schroeder, Jeremy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ingason, Arni Sigurdur
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Birch, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Beware of poor-quality MgO substrates: A study of MgO substrate quality and its effect on thin film quality2015Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 420, s. 22-31Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnesium oxide (MgO) substrates are widely used for fundamental research of a large variety of materials. Our motivation is to make the research community aware of poor-quality MgO substrates. We acquired thirty MgO substrates from six different vendors and demonstrate that single-crystal MgO substrates are not always single crystal, but can consist of multiple domains. These multiple-domain MgO substrates can have a significant impact on research results as demonstrated by a one-to-one correlation between the domain structure of MgO substrates and titanium nitride (TiN) thin films (i.e. poor-quality MgO substrates result in poor-quality TiN films). Poor-quality MgO substrates are shown to be a widespread problem with over 70% of the evaluated substrates exhibiting multiple domains, essentially disqualifying them as substrates for epitaxy. MgO substrate vendors and researchers are encouraged to work together to resolve the problem of inconsistent MgO substrate quality and the research community is encouraged to perform quality control of MgO substrates prior to thin film deposition. Quality control by vendors and/or researchers can be achieved by acquiring X-ray diffraction omega-phi maps in batch processes, as detailed in this paper. We also propose a simple quality grading system to differentiate MgO substrates of varying quality.

  • 78.
    Thore, Andreas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Alling, Björn
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    First-principles calculations of the electronic, vibrational, and elastic properties of the magnetic laminate Mn2GaC2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, nr 10, s. 103511-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we report the by first-principles predicted properties of the recently discovered magnetic MAX phase Mn2GaC. The electronic band structure and vibrational dispersion relation, as well as the electronic and vibrational density of states, have been calculated. The band structure close to the Fermi level indicates anisotropy with respect to electrical conductivity, while the distribution of the electronic and vibrational states for both Mn and Ga depend on the chosen relative orientation of the Mn spins across the Ga sheets in the Mn–Ga–Mn trilayers. In addition, the elastic properties have been calculated, and from the five elastic constants, the Voigt bulk modulus is determined to be 157 GPa, the Voigt shear modulus 93 GPa, and the Young's modulus 233 GPa. Furthermore, Mn2GaC is found relatively elastically isotropic, with a compression anisotropy factor of 0.97, and shear anisotropy factors of 0.9 and 1, respectively. The Poisson's ratio is 0.25. Evaluated elastic properties are compared to theoretical and experimental results for M 2 AC phases where M = Ti, V, Cr, Zr, Nb, Ta, and A = Al, S, Ge, In, Sn

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  • 79.
    Thore, Andreas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Alling, Björn
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Magnetic exchange interactions and critical temperature of the nanolaminate Mn2GaC from first-principles supercell methods2016Ingår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 93, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we employ and critically evaluate a first-principles approach based on supercell calculations for predicting the magnetic critical order-disorder temperature 𝑇𝑐 . As a model material we use the recently discovered nanolaminate Mn2GaC.

    First, we derive the exchange interaction parameters 𝐽𝑖𝑗 between pairs of Mn atoms on sites 𝑖 and 𝑗 of the bilinear Heisenberg Hamiltonian using the novel magnetic direct cluster averaging method (MDCA), and then compare the 𝐽’s from the MDCA calculations to the same parameters calculated using the Connolly-Williams method. We show that the two methods yield closely matching results, but observe that the MDCA method is computationally less effective when applied to highly ordered phases such as Mn2GaC.

    Secondly, Monte Carlo simulations are used to derive the magnetic energy, specific heat, and 𝑇𝑐 . For Mn2GaC, we find 𝑇𝑐 = 660 K. The uncertainty in the calculated 𝑇𝑐 caused by possible uncertainties in the 𝐽’s is discussed and exemplified in our case by an analysis of the impact of the statistical uncertainties of the MDCA-derived 𝐽’s, resulting in a 𝑇𝑐 distribution with a standard deviation of 133 K.

  • 80.
    Thore, Andreas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Alling, Björn
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Max Planck Institute Eisenforsch GmbH, Germany.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Phase stability of the nanolaminates V2Ga2C and (Mo1-xVx)(2)Ga2C from first-principles calculations2016Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, nr 18, s. 12682-12688Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We here use first-principles calculations to investigate the phase stability of the hypothetical laminated material V2Ga2C and the related alloy (Mo1-xVx)(2)Ga2C, the latter for a potential parent material for synthesis of (Mo1-xVx)(2)C, a new two-dimensional material in the family of so called MXenes. We predict that V2Ga2C is thermodynamically stable with respect to all identified competing phases in the ternary V-Ga-C phase diagram. We further calculate the stability of ordered and disordered configurations of Mo and V in (Mo1-xVx)(2)Ga2C and predict that ordered (Mo1-xVx)(2)Ga2C for x <= 0.25 is stable, with an order-disorder transition temperature of similar to 1000 K. Furthermore, (Mo1-xVx)(2)Ga2C for x = 0.5 and x >= 0.75 is suggested to be stable, but only for disordered Mo-V configurations, and only at elevated temperatures. We have also investigated the electronic and elastic properties of V2Ga2C; the calculated bulk, shear, and Youngs modulus are 141, 94, and 230 GPa, respectively.

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  • 81.
    Thore, Andreas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Alling, Björn
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Phase stability of the nanonlaminates V2Ga2C and (Mo1-xVx)2Ga2C from first-principles calculations2016Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    We here use first-principles calculations to investigate the phase stability of the hypothetical laminated materials V2Ga2C and the related alloy (Mo1-xVx)2Ga2C, the latter for a potential parent material for synthesis of (Mo1-xVx)2C, a new two-dimensional material in the family of so called MXenes. We predict that V2Ga2C is thermodynamically stable with respect to all identified competing phases in the ternary VGa-C phase diagram. We further predict the stability for ordered and disordered configurations of Mo and V in (Mo1-xVx)2Ga2C and predict that ordered (Mo1-xVx)2Ga2C for 𝑥 ≤ 0.25 is stable, with an orderdisorder transition temperature of ~1000 K. Furthermore, (Mo1-xVx)2Ga2C for 𝑥 = 0.5 and 𝑥 ≥ 0.75 is suggested to potentially be stable, but only for disordered Mo-V configurations, and only at elevated temperatures. We have also investigated the electronic and elastic properties of V2Ga2C; the calculated bulk, shear, and Young’s modulus are 141, 95, and 232 GPa, respectively.

  • 82.
    Thore, Andreas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Alling, Björn
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Temperature dependent phase stability of nanolaminated ternaries from first-principles calculations2014Ingår i: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 91, s. 251-257Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methods based on first-principles calculations have proven effective for predicting the thermodynamic stability of materials that have not previously been considered. However, the vast majority of these predictions are based on 0 K calculations, which means that little is known about the effects of temperature on their accuracy. This causes considerable uncertainty with respect to stability predictions of new hypothetical phases. In this work we combine first-principles calculations with an optimization procedure to calculate the phase stability as a function of temperature for Ti2AlC, Ti3AlC2 and Ti4AlC3 MAX phases with respect to their most competing phases in the Ti-Al-C phase diagram, in a temperature interval from 0 to 2000 K. To model nonzero temperatures, we include effects from the electronic and vibrational free energies to the Gibbs free energy for all relevant competing phases. We show that, due to a mutual cancellation of the temperature dependent energy terms, the results of neither the harmonic nor the quasiharmonic calculations differ significantly from the calculated 0 K formation energies. We thus provide a plausible explanation for the success of previous 0 K predictions, an explanation which also serves as evidence for the hypothesis that the phase stability in many materials systems is primarily governed by the 0 K energy terms.

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  • 83.
    Tucker, Mark
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Czigany, Zsolt
    Research Institute for Technical Physics and Materials Science, RCNS, Budapest, Hungary.
    Broitman, Esteban
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Näslund, Lars-Åke
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Filtered pulsed cathodic arc deposition of fullerene-like carbon and carbon nitride films2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 14, s. 144312-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Carbon and carbon nitride films (CNx , 0 ≤ x ≤ 0.26) were deposited by filtered pulsed cathodic arc and were investigated using transmission electron microscopy and X-ray photoelectron spectroscopy. A “fullerene-like” (FL) structure of ordered graphitic planes, similar to that of magnetron sputtered FL-CNx films, was observed in films deposited at 175 °C and above, with N2 pressures of 0 and 0.5 mTorr. Higher substrate temperatures and significant nitrogen incorporation are required to produce similar FL structure by sputtering, which may, at least in part, be explained by the high ion charge states and ion energies characteristic of arc deposition. A gradual transition from majority sp3-hybridized films to sp2 films was observed with increasing substrate temperature. High elastic recovery, an attractive characteristic mechanical property of FL-CNx films, is evident in arc-deposited films both with and without nitrogen content, and both with and without FL structure.

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  • 84.
    Tucker, Mark D
    et al.
    University of Sydney.
    Persson, Per
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Guenette, Mathew C
    University of Sydney.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Bilek, Marcela M M
    University of Sydney.
    McKenzie, David R
    University of Sydney.
    Substrate orientation effects on the nucleation and growth of the M(n+1)AX(n) phase Ti2AlC2011Ingår i: JOURNAL OF APPLIED PHYSICS, ISSN 0021-8979, Vol. 109, nr 1, s. 014903-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The M(n+1)AX(n) (MAX) phases are ternary compounds comprising alternating layers of a transition metal carbide or nitride and a third "A-group" element. The effect of substrate orientation on the growth of Ti2AlC MAX phase films was investigated by studying pulsed cathodic arc deposited samples grown on sapphire cut along the (0001), (10 (1) over bar0), and (1 (1) over bar 02) crystallographic planes. Characterization of these samples was by x-ray diffraction, atomic force microscopy, and cross-sectional transmission electron microscopy. On the (10 (1) over bar0) substrate, tilted (10 (1) over bar8) growth of Ti2AlC was found, such that the TiC octahedra of the MAX phase structure have the same orientation as a spontaneously formed epitaxial TiC sublayer, preserving the typical TiC-Ti2AlC epitaxial relationship and confirming the importance of this relationship in determining MAX phase film orientation. An additional component of Ti2AlC with tilted fiber texture was observed in this sample; tilted fiber texture, or axiotaxy, has not previously been seen in MAX phase films.

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  • 85.
    Zhirkov, Igor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Eriksson, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Petruhins, Andrejs
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ingason, Arni Sigurdur
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Effect of Ti-Al cathode composition on plasma generation and plasma transport in direct current vacuum arc2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 12, s. 123301-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    DC arc plasma from Ti, Al, and Ti1-xAlx (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes was characterized with respect to plasma chemistry and charge-state-resolved ion energy. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the deposited films and the cathode surfaces were used for exploring the correlation between cathode-, plasma-, and film composition. Experimental work was performed at a base pressure of 10(-6) Torr, to exclude plasma-gas interaction. The plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the cathode composition, while deposited films were in accordance with the cathode stoichiometry. This may be explained by presence of neutrals in the plasma/vapour phase. The average ion charge states (Ti = 2.2, Al = 1.65) were consistent with reference data for elemental cathodes, and approximately independent on the cathode composition. On the contrary, the width of the ion energy distributions (IEDs) were drastically reduced when comparing the elemental Ti and Al cathodes with Ti0.5Al0.5, going from similar to 150 and similar to 175 eV to similar to 100 and similar to 75 eV for Ti and Al ions, respectively. This may be explained by a reduction in electron temperature, commonly associated with the high energy tail of the IED. The average Ti and Al ion energies ranged between similar to 50 and similar to 61 eV, and similar to 30 and similar to 50 eV, respectively, for different cathode compositions. The attained energy trends were explained by the velocity rule for compound cathodes, which states that the most likely velocities of ions of different mass are equal. Hence, compared to elemental cathodes, the faster Al ions will be decelerated, and the slower Ti ions will be accelerated when originating from compound cathodes. The intensity of the macroparticle generation and thickness of the deposited films were also found to be dependent on the cathode composition. The presented results may be of importance for choice of cathodes for thin film depositions involving compound cathodes.

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  • 86.
    Zhirkov, Igor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Eriksson, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ion velocities in direct current arc plasma generated from compound cathodes2111022013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, nr 21, s. 213302-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Arc plasma from Ti-C, Ti-Al, and Ti-Si cathodes was characterized with respect to charge-state-resolved ion energy. The evaluated peak velocities of different ion species in plasma generated from a compound cathode were found to be equal and independent on ion mass. Therefore, measured difference in kinetic energies can be inferred from the difference in ion mass, with no dependence on ion charge state. The latter is consistent with previous work. These findings can be explained by plasma quasineutrality, ion acceleration by pressure gradients, and electron-ion coupling. Increasing the C concentration in Ti-C cathodes resulted in increasing average and peak ion energies for all ion species. This effect can be explained by the "cohesive energy rule," where material and phases of higher cohesive energy generally result in increasing energies (velocities). This is also consistent with the here obtained peak velocities around 1.37, 1.42, and 1.55 (10(4) m/s) for ions from Ti0.84Al0.16, Ti0.90Si0.10, and Ti0.90C0.10 cathodes, respectively.

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  • 87.
    Zhirkov, Igor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Oks, Efim
    Institute High Current Elect SB RAS, Russia.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Effect of N-2 and Ar gas on DC arc plasma generation and film composition from Ti-Al compound cathodes2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, nr 21, s. 213301-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    DC arc plasma from Ti, Al, and Ti(1-x)A(l)x (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes has been characterized with respect to plasma chemistry (charged particles) and charge-stateresolved ion energy for Ar and N-2 pressures in the range 10(-6) to 3 x 10(-2) Torr. Scanning electron microscopy was used for exploring the correlation between the cathode and film composition, which in turn was correlated with the plasma properties. In an Ar atmosphere, the plasma ion composition showed a reduction of Al of approximately 5 at.% compared to the cathode composition, while deposited films were in accordance with the cathode stoichiometry. Introducing N-2 above similar to 5 x 10(-3) Torr, lead to a reduced Al content in the plasma as well as in the film, and hence a 1:1 correlation between the cathode and film composition cannot be expected in a reactive environment. This may be explained by an influence of the reactive gas on the arc mode and type of erosion of Ti and Al rich contaminations, as well as on the plasma transport. Throughout the investigated pressure range, a higher deposition rate was obtained from cathodes with higher Al content. The origin of generated gas ions was investigated through the velocity rule, stating that the most likely ion velocities of all cathode elements from a compound cathode are equal. The results suggest that the major part of the gas ions in Ar is generated from electron impact ionization, while gas ions in a N-2 atmosphere primarily originate from a nitrogen contaminated layer on the cathode surface. The presented results provide a contribution to the understanding processes of plasma generation from compound cathodes. It also allows for a more reasonable approach to the selection of composite cathode and experimental conditions for thin film depositions. (C) 2015 AIP Publishing LLC.

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  • 88.
    Zhirkov, Igor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Oks, Efim
    Institute High Current Elect SB RAS, Russia.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Experimentally established correlation between ion charge state distributions and kinetic ion energy distributions in a direct current vacuum arc discharge2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, nr 9, s. 093301-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    DC arc plasmas from Al, Ti, Cu, Mo, and W cathodes have been characterized with respect to plasma chemistry and charge-state-resolved ion energy. The evaluated average ionization energies in the plasmas were found to be linearly correlated with the kinetic ion energies. This was further supported by evaluation of previously published data for 42 elements. A comparison of the total ion kinetic energy distribution and the corresponding ion charge state distribution, as defined by the ionization energies of the constituent ions, showed close to equivalent shapes and widths, for all cathodes analyzed. This suggests that the energy provided for ionization and acceleration varies simultaneously during plasma generation in the arc spot. The presented results provide a link between the ionization and acceleration processes, and may provide further insight into the fundamentals of cathode spot evolution and plasma generation. (C) 2015 AIP Publishing LLC.

  • 89.
    Zhirkov, Igor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Petruhins, Andrejs
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Näslund, Lars-Åke
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Kolozsvari, Szilard
    PLANSEE Composite Mat GmbH, Germany.
    Polcik, Peter
    PLANSEE Composite Mat GmbH, Germany.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Vacuum arc plasma generation and thin film deposition from a TiB2 cathode2015Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, nr 18, s. 184103-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied the utilization of TiB2 cathodes for thin film deposition in a DC vacuum arc system. We present a route for attaining a stable, reproducible, and fully ionized plasma flux of Ti and B by removal of the external magnetic field, which leads to dissipation of the vacuum arc discharge and an increased active surface area of the cathode. Applying a magnetic field resulted in instability and cracking, consistent with the previous reports. Plasma analysis shows average energies of 115 and 26 eV, average ion charge states of 2.1 and 1.1 for Ti and B, respectively, and a plasma ion composition of approximately 50% Ti and 50% B. This is consistent with measured resulting film composition from X-ray photoelectron spectroscopy, suggesting a negligible contribution of neutrals and macroparticles to the film growth. Also, despite the observations of macroparticle generation, the film surface is very smooth. These results are of importance for the utilization of cathodic arc as a method for synthesis of metal borides. (C) 2015 AIP Publishing LLC.

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  • 90.
    Zhirkov, Igor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Petruhins, Andrejs
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Polcik, Peter
    PLANSEE Composite Mat GmbH, Germany.
    Kolozsvari, Szilard
    PLANSEE Composite Mat GmbH, Germany.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Generation of super-size macroparticles in a direct current vacuum arc discharge from a Mo-Cu cathode2016Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, nr 5, s. 054103-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An inherent property of cathodic arc is the generation of macroparticles, of a typical size ranging from submicrometer up to a few tens of mu m. In this work, we have studied macroparticle generation from a Mo0.78Cu0.22 cathode used in a dc vacuum arc discharge, and we present evidence for super-size macroparticles of up to 0.7mm in diameter. All analyzed particles are found to be rich in Mo (>= 98 at. %). The particle generation is studied by visual observation of the cathode surface during arcing, by analysis of composition and geometrical features of the used cathode surface, and by examination of the generated macroparticles with respect to shape and composition. A mechanism for super-size macroparticle generation is suggested based on observed segregated layers of Mo and Cu identified in the topmost part of the cathode surface, likely due to the discrepancy in melting and evaporation temperatures of Mo and Cu. The results are of importance for increasing the fundamental understanding of macroparticle generation, which in turn may lead to increased process control and potentially provide paths for tuning, or even mitigating, macroparticle generation. (C) 2016 AIP Publishing LLC.

  • 91.
    Zhu, Jianqiang
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska högskolan.
    Eriksson, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ghafoor, Naureen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Johansson, M P
    SECO Tools AB.
    Sjolen, J
    SECO Tools AB.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Odén, Magnus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska högskolan.
    Characterization of worn Ti-Si cathodes used for reactive cathodic arc evaporation2010Ingår i: JOURNAL OF VACUUM SCIENCE and TECHNOLOGY A, ISSN 0734-2101, Vol. 28, nr 2, s. 347-353Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The microstructural evolution of Ti1-xSix cathode surfaces (x=0, 0.1, 0.2) used in reactive cathodic arc evaporation has been investigated by analytical electron microscopy and x-ray diffractometry. The results show that the reactive arc operated in N-2 atmosphere induces a 2-12 mu m thick N-containing converted layer consisting of nanosized grains in the two-phase Ti and Ti5Si3 cathode surface. The formation mechanism of this layer is proposed to be surface nitriding and redeposition of macroparticles formed during the deposition process. The surface roughness of the worn Ti1-xSix cathodes increases with increasing Si content, up to 20 at. %, due to preferential erosion of Ti5Si3.

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  • 92.
    Zhu, Jianqiang
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska högskolan.
    Eriksson, Anders O.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ghafoor, Naureen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska högskolan.
    Greczynski, Grzegorz
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Odén, Magnus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska högskolan.
    Microstructure evolution of Ti3SiC2 compound cathodes during reactive cathodic arc evaporation2011Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 29, nr 3, s. 031601-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The microstructure evolution and compositional variation of Ti3SiC2 cathode surfaces during reactive cathodic arc evaporation are presented for different process conditions. The results show that phase decomposition takes place in the near-surface region, resulting in a 5-50 mu m thick converted layer that is affected by the presence of nitrogen in the deposition chamber. This layer consists of two different sublayers, i.e., 1-20 mu m thick top layer with a melted and resolidified microstructure, followed by a 4-30 mu m thick transition layer with a decomposed microstructure. The converted layer contains a polycrystalline TiCx phase and trace quantities of Si-rich domains with Ti5Si3(C) at their interface. The arc discharge causes Si redistribution in the two regions of the layer, whose Si/(Ti+Si) ratio is higher in the top region and lower in the transition region compared to the virgin material.

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