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  • 1.
    Adam, Stefan
    et al.
    Leibniz Institute Polymerforsch eV, Germany; Technical University of Dresden, Germany.
    Koenig, Meike
    Leibniz Institute Polymerforsch eV, Germany; Technical University of Dresden, Germany; Karlsruhe Institute Technology, Germany.
    Rodenhausen, Keith Brian
    University of Nebraska, NE 68588 USA; Biolin Science Inc, NJ 07652 USA.
    Eichhorn, Klaus-Jochen
    Leibniz Institute Polymerforsch eV, Germany.
    Oertel, Ulrich
    Leibniz Institute Polymerforsch eV, Germany.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Leibniz Institute Polymerforsch eV, Germany; University of Nebraska, NE 68588 USA; University of Nebraska, NE 68588 USA.
    Stamm, Manfred
    Leibniz Institute Polymerforsch eV, Germany; Technical University of Dresden, Germany.
    Uhlmann, Petra
    Leibniz Institute Polymerforsch eV, Germany; University of Nebraska, NE 68588 USA.
    Quartz crystal microbalance with coupled Spectroscopic Ellipsometry-study of temperature-responsive polymer brush systems2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 843-851Article in journal (Refereed)
    Abstract [en]

    Using a combined setup of quartz crystal microbalance with dissipation monitoring together with spectroscopic ellipsometry, the thermo-responsive behavior of two different brush systems (poly(N-isopropyl acrylamide) and poly(2-oxazoline)s) was investigated and compared to the behavior of the free polymer in solution. Poly(2-oxazoline)s with three different hydrophilicities were prepared by changing the content of a hydrophilic comonomer. While both polymer types exhibit a sharp, discontinuous thermal transition in solution, in the brush state the transition gets broader in the case of poly(N-isopropyl acrylamide) and is transformed into a continuous transition for poly(2-oxazoline)s. The position of the transition in solution is influenced by the degree of hydrophilicity of the poly(2-oxazoline). The difference in areal mass detected by quartz crystal microbalance and by spectroscopic ellipsometry, has been attributed to the chain segment density profile of the polymer brushes. Applying this density profile information, for poly(N-isopropyl acrylamide) two different swelling stages could be identified, while for poly(2-oxazoline) the transition between a parabolic and more step-wise profile is found continuous. The different swelling characteristics were attributed to the different miscibility behavior types, with the brush state acting similar to a crosslinked system. (C) 2017 Elsevier B.V. All rights reserved.

  • 2. Amandusson, H.
    et al.
    Ekedahl, Lars-Gunnar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Dannetun, Helen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Effect of CO and O2 on hydrogen permeation through a palladium membrane2000In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 153, no 4, p. 259-267Article in journal (Refereed)
    Abstract [en]

    Hydrogen permeation through a 25-µm thick palladium membrane during continuous exposures of hydrogen together with different combinations of oxygen and carbon monoxide has been studied at membrane temperatures of 100 °C-250 °C (total pressures of 40-150 Torr). Both CO and O2, individually, inhibit hydrogen permeation through the membrane. The cause of the inhibition is, however, somewhat different. CO blocks available hydrogen dissociation sites, while oxygen both blocks dissociation sites and also consumes adsorbed hydrogen through the production of water. When a combination of CO and O2 is supplied together with hydrogen, new reaction pathways will emerge. The carbon dioxide formation will dominate the water forming reaction, and consequently, the blocking effect caused by the formation of water will be suppressed. In a mixture of CO+O2+H2, the hydrogen permeation can become either larger or smaller than that due to only O2+H2 or CO+H2 depending on the CO/O2 ratio. It is thus possible to find a situation where carbon monoxide and oxygen react to form CO2 leaving adsorbed hydrogen free to permeate the membrane.

  • 3.
    Armakavicius, Nerijus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Bouhafs, Chamseddine
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Stanishev, Vallery
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Kühne, Philipp
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Knight, Sean
    Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA.
    Hofmann, Tino
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA / Department of Physics and Optical Science, University of North Carolina at Charlotte, USA.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 357-360Article in journal (Refereed)
    Abstract [en]

    Cavity-enhanced optical Hall effect at terahertz (THz) frequencies is employed to determine the free charge carrier properties in epitaxial graphene (EG) with different number of layers grown by high-temperature sublimation on 4H-SiC(0001). We find that one monolayer (ML) EG possesses p-type conductivity with a free hole concentration in the low 1012 cmᅵᅵᅵ2 range and a free hole mobility parameter as high as 1550 cm2/Vs. We also find that 6 ML EG shows n-type doping behavior with a much lower free electron mobility parameter of 470 cm2/Vs and an order of magnitude higher free electron density in the low 1013 cmᅵᅵᅵ2 range. The observed differences are discussed. The cavity-enhanced THz optical Hall effect is demonstrated to be an excellent tool for contactless access to the type of free charge carriers and their properties in two-dimensional materials such as EG.

  • 4.
    Bertuccio, Giuseppe
    et al.
    Politecnico di Milano, Como Campus, Italy.
    Puglisi, Donatella
    Politecnico di Milano, Como Campus, Italy.
    Torrisi, Lorenzo
    University of Messina, Italy.
    Lanzieri, Claudio
    Selex Sistemi Integrati S.p.A., Rome, Italy.
    Silicon carbide detector for laser-generated plasma radiation2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 272, p. 128-131Article in journal (Refereed)
    Abstract [en]

    We present the performance of a Silicon Carbide (SiC) detector in the acquisition of the radiation emittedby laser generated plasmas. The detector has been employed in time of flight (TOF) configuration withinan experiment performed at the Prague Asterix Laser System (PALS). The detector is a 5 mm2 area 100 nmthick circular Ni SiC Schottky junction on a high purity 4H-SiC epitaxial layer 115 μm thick. Currentsignals from the detector with amplitudes up to 1.6 A have been measured, achieving voltage signals over 80 V on a 50 Ω load resistance with excellent signal to noise ratios. Resolution of few nanoseconds hasbeen experimentally demonstrated in TOF measurements. The detector has operated at 250 V DC biasunder extreme operating conditions with no observable performance degradation.

  • 5.
    Bjorklund, Robert
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Karlsson, Susanne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Borén, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Organic Analytical Chemistry .
    Allard, E
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Linkoping Univ, Dept Water & Environm Studies, S-58183 Linkoping, Sweden.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Photodesorption of fulvic acid from iron oxide surfaces into aqueous solutions2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 174, no 2, p. 166-175Article in journal (Refereed)
    Abstract [en]

    Photodesorption of thin films of fulvic acid adsorbed on planar iron oxide surfaces was monitored by ellipsometry. Description was first observed at 546 nm, and additional fractions of the adsorbed acid left the surfaces at 405 and 365 nm Similar kinetics for photodesorption was observed from metallic iron films and from porous iron oxide prepared electrochemically by deposition on porous silicon substrates. Soluble photoproducts leaving the surface H ere monitored by UV absorbance spectroscopy at 200 nm Gaseous products were not detected by mass spectrometry but the results seemed to indicate that net all of the photoproducts entered the liquid phase. Of the metal films tested which adsorbed fulvic acid from aqueous solution (Fe. Cr, Ni, Al, and Pt), it was only iron which exhibited a photodesorption effect. (C) 2001 Elsevier Science B.V. All rights reserved.

  • 6.
    Briley, Chad
    et al.
    University of Nebraska, NE 68588 USA.
    Mock, Alyssa
    University of Nebraska, NE 68588 USA.
    Korlacki, Rafal
    University of Nebraska, NE 68588 USA.
    Hofmann, Tino
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska, NE 68588 USA.
    Schubert, Eva
    University of Nebraska, NE 68588 USA.
    Schubert, Mathias
    University of Nebraska, NE 68588 USA.
    Effects of annealing and conformal alumina passivation on anisotropy and hysteresis of magneto-optical properties of cobalt slanted columnar thin films2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 320-324Article in journal (Refereed)
    Abstract [en]

    We present magneto-optical dielectric tensor data of cobalt and cobalt oxide slanted columnar thin films obtained by vector magneto-optical generalized ellipsometry. Room-temperature hysteresis magnetization measurements were performed in longitudinal and polar Kerr geometries on samples prior to and after a heat treatment process with and without a conformal Al2O3 passivation coating. The samples have been characterized by generalized ellipsometry, scanning electron microscopy, and Raman spectroscopy in conjuncture with density functional theory. We observe strongly anisotropic hysteresis behaviors, which depend on the nanocolumn and magnetizing field orientations. We find that deposited cobalt films that have been exposed to heat treatment and subsequent atmospheric oxidation into Co3O4, when not conformally passivated, reveal no measurable magneto-optical properties while cobalt films with passivation coatings retain highly anisotropic magneto-optical properties (C) 2016 Published by Elsevier B.V.

  • 7.
    Bukaluk, A.
    et al.
    Instytut Matematyki I Fizyki, Akademia Techniczno-Rolnicza, Ul. K., Bydgoszcz, Poland.
    Wronkowska, A.A.
    Instytut Matematyki I Fizyki, Akademia Techniczno-Rolnicza, Ul. K., Bydgoszcz, Poland.
    Wronkowski, A.
    Instytut Matematyki I Fizyki, Akademia Techniczno-Rolnicza, Ul. K., Bydgoszcz, Poland.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Firszt, F.
    Instytut Fizyki, Uniw. Mikolaja Kopernika, Ul. G., Torun, Poland.
    Legowski, S.
    Instytut Fizyki, Uniw. Mikolaja Kopernika, Ul. G., Torun, Poland.
    Meczynska, H.
    Meczynska, H., Instytut Fizyki, Uniw. Mikolaja Kopernika, Ul. G., Torun, Poland.
    Szatkowski, J.
    Instytut Fizyki, Uniw. Mikolaja Kopernika, Ul. G., Torun, Poland.
    Auger electron spectroscopy, ellipsometry and photoluminescence investigations of Zn1-XBeXSe alloys2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 175-176, p. 531-537Article in journal (Refereed)
    Abstract [en]

    In this paper, properties of the Zn1-XBeXSe crystals grown from the melt by the high-pressure Bridgman method are reported. Spectroscopic ellipsometry has been used for determination of the complex dielectric function of Zn1-XBeXSe. On the basis of the photon energy dependence of the dielectric function, the energy gaps of alloys containing different beryllium concentrations have been evaluated. Measurements of the photoluminescence (PL) spectra allowed to find the excitonic gap in the investigated alloys. Auger electron spectroscopy (AES) with simultaneous argon ion sputtering has been used for determination of surface composition. AES investigations allowed to make predictions concerning distribution of particular elements in the samples. © 2001 Elsevier Science B.V.

  • 8.
    Chen, Ruei-San
    et al.
    National Taiwan University of Science and Technology, Taiwan.
    Tang, Chih-Che
    Department of Electronic Engineering, National Taiwan University of Science and Technology, Taiwan.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Holtz, Per Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Electronic transport properties in aluminum indium nitride nanorods grown by magnetron sputter epitaxy2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 285, p. 625-628Article in journal (Refereed)
    Abstract [en]

    The electronic transport properties of the wide-bandgap aluminum indium nitride (AlInN) nanorods (NRs) grown by ultrahigh-vacuum magnetron sputter epitaxy (MSE) have been studied. The conductivities of the ternary compound nanostructure locates at the value of 15 Q-1 cm -1, which is respectively one and two orders of magnitude lower than the binary GaN and InN counterparts grown by chemical vapor deposition (CVD). The very shallow donor level/band with the activation energy at 11 + 2 meV was obtained by the temperature-dependent measurement. In addition, the photoconductivity has also been investigated. The photoconductive (PC) gain of the NRs device can reach near 2400 under a low bias at 0.1 V and the light intensity at 100W m-2 for ultraviolet response in vacuum. The power-insensitive gain and ambience-dependent photocurrent are also observed, which is attributed to the probable surfacecontrolled PC mechanism in this ternary nitride nanostructure.

  • 9.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    The relative ionization gauge sensitivity of some unsaturated hydrocarbons1987In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 29, p. 331-Article in journal (Refereed)
    Abstract [en]

    By studying the water desorption rate from an oxygen covered Pd surface which is exposed to some unsaturated hydrocarbons (and hydrogen) the relative ionization gauge sensitivity of the hydrocarbons: acetylene, ethylene, propene, 1- and 2-butene, propadiene, 1,3-butadiene, propyne and butyne has been determined.

  • 10.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Söderberg, D.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    A hydrogen-sensitive Pd-MOS structure working over a wide pressure range1984In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 17, p. 259-Article in journal (Refereed)
    Abstract [en]

    A Pd-MOS structure has been developed which has proven to be sensitive to hydrogen both in air at atmospheric pressures and in UHV. The ability to work over a wide pressure range makes it an interesting component in, e.g., the study of catalytic reactions involving hydrogen on metal surfaces. Here we demonstrate the hydrogen sensitivity of such a structure over a pressure range of 5x10-11 to 2 Torr.

  • 11.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Real time measurements of hydrogen desorption and absorption during CO exposures of Pd: Hydrogen sticking and dissolution1998In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 133, no 1-2, p. 89-97Article in journal (Refereed)
    Abstract [en]

    Combined real time measurements of hydrogen desorption and absorption show that both processes may be induced simultaneously by CO adsorption on a hydrogen-covered Pd surface. The induced absorption is found to be a kinetic effect, where the amount absorbed depends on the hydrogen desorption rate and the CO adsorption rate. In addition to simple site blocking, adsorbed CO induces an increase in the hydrogen desorption energy and an activation barrier for hydrogen dissociation. Both increase linearly with CO coverage for θCO>0.18 ML. Below this coverage, the hydrogen dissociation is non-activated.

  • 12.
    Gervacio-Arciniega, J. J.
    et al.
    University of Nacl Autonoma Mexico, Mexico.
    Flores-Ruiz, F. J.
    University of Nacl Autonoma Mexico, Mexico.
    Diliegros-Godines, C. J.
    University of Nacl Autonoma Mexico, Mexico.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Enriquez-Flores, C. I.
    CINVESTAV, Mexico.
    Espinoza-Beltran, F. J.
    CINVESTAV, Mexico.
    Siqueiros, J.
    University of Nacl Autonoma Mexico, Mexico.
    Cruz, M. P.
    University of Nacl Autonoma Mexico, Mexico.
    Nanofrictional behavior of amorphous, polycrystalline and textured Y-Cr-O films2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 378, p. 157-162Article in journal (Refereed)
    Abstract [en]

    Differences in friction coefficients (mu) of ferroelectric YCrO3, textured and polycrystalline films, and non-ferroelectric Y-Cr-O films are analyzed. The friction coefficient was evaluated by atomic force microscopy using a simple quantitative procedure where the dependence of friction force with the applied load is obtained in only one topographical image. A simple code was developed with the MATLAB (R) software to analyze the experimental data. The code includes a correction of the hysteresis in the forward and backward scanning directions. The quantification of load exerted on the sample surface was obtained by finite element analysis of the AFM cantilever starting from its experimental dynamic information. The results show that the ferroelectric YCrO3 film deposited on a Pt(150 nm)/TiO2(30 nm)/SiO2/Si (100) substrate is polycrystalline and has a lower friction coefficient than the deposited on SrTiO3 (110), which is highly textured. From a viewpoint of industrial application in ferroelectric memories, where the writing process is electrical or mechanically achieved by sliding AFM tips on the sample, polycrystalline YCrO3 films seem to be the best candidates due to their lower mu, (C) 2016 Elsevier B.V. All rights reserved.

  • 13.
    Gervilla Palomar, Victor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Almyras, Georgios
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Thunstrom, F.
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Dynamics of 3D-island growth on weakly-interacting substrates2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 488, p. 383-390Article in journal (Refereed)
    Abstract [en]

    The growth dynamics of faceted three-dimensional (3D) Ag islands on weakly-interacting substrates are investigated-using kinetic Monte Carlo (kMC) simulations and analytical modelling-with the objective of determining the critical top-layer radius R-c required to nucleate a new island layer as a function of temperature T, at a constant deposition rate. kMC shows that R-c decreases from 17.3 to 6.0 angstrom as T is increased at 25 K intervals, from 300 to 500 K. That is, a higher T promotes top-layer nucleation resulting in an increase in island height-to-radius aspect ratios. This explains experimental observations for film growth on weakly-interacting substrates, which are not consistent with classical homoepitaxial growth theory. In the latter case, higher temperatures yield lower top-layer nucleation rates and lead to a decrease in island aspect ratios. The kMC simulation results are corroborated by an analytical mean field model, in which R-c is estimated by calculating the steady-state adatom density on the island side facets and top layer as a function of T. The overall findings of this study constitute a first step toward developing rigorous theoretical models, which can be used to guide synthesis of metal nanostructures, and layers with controlled shape and morphology, on technologically important substrates, including two-dimensional crystals, for nanoelectronic and catalytic applications.

    The full text will be freely available from 2021-05-22 07:54
  • 14. Greczynski, G.
    et al.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Experimental study of poly(9,9-dioctyl-fluorene) and its interface with Li and LiF2000In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 166, no 1, p. 380-386Article in journal (Refereed)
    Abstract [en]

    The chemical and electronic structure of a new conjugated polymer, poly(9,9-dioctyl-fluorene) (PFO), has been studied by photoelectron spectroscopy. The polymer films were free of oxygen contamination (within the detection limits of photoelectron spectroscopy). X-ray and ultraviolet photoelectron spectroscopy was carried out on Li- and LiF-deposition on PFO as well as on LiF-deposition on aluminum. In the case of Li-deposition on PFO films, doping occurred resulting in the formation of polaronic charge carriers at low doping levels and bipolaronic charge carriers at high doping levels. LiF-deposition on PFO did not cause doping of the polymer films, nor did the LiF dissociate at the interface. No significant shifts in binding energy (BE) or work function occurred. LiF-deposition on sputter-cleaned aluminum showed evidence of surface dipole formation, though LiF dissociation was not detected. Al-deposition on LiF/PFO films did not cause dissociation of LiF, unlike the case in Alq3.

  • 15. Greczynski, G.
    et al.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    An experimental study of poly(9,9-dioctyl-fluorene) and its interfaces with Al, LiF and CsF2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 175-176, p. 319-325Article in journal (Refereed)
    Abstract [en]

    Sandwich-style interfaces of Al/LiF/poly(9,9-dioctyl-fluorene) and Al/CsF/poly(9,9-dioctyl-fluorene) have been studied using X-ray and ultraviolet photoelectron spectroscopy. The polymer films were free of oxygen contamination (within the detection limits of photoelectron spectroscopy). In the case of LiF-deposition on poly(9,9-dioctyl-fluorene) films, doping did not occur, nor did the LiF dissociate upon Al-deposition. No significant shifts in a binding energy of the core levels, nor any changes in the work function were detected. However, for the Al/LiF/poly(9,9-dioctyl-fluorene) interface, there was no degradation of the p-electronic structure, unlike the case for Al deposited directly unto poly(9,9-dioctyl-fluorene). For the Al/CsF/poly(9,9-dioctyl-fluorene) interface, the CsF dissociated upon Al-deposition, with the Cs likely n-doping, the polymer at the interface. When deposited onto an Al surface, CsF also were found to dissociate at the interface but remaining in the CsF form away from the Al surface. © 2001 Elsevier Science B.V.

  • 16.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Reliable determination of chemical state in x-ray photoelectron spectroscopy based on sample-work-function referencing to adventitious carbon: Resolving the myth of apparent constant binding energy of the C 1s peak2018In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 451, p. 99-103Article in journal (Refereed)
    Abstract [en]

    The accuracy of chemical-state determination by x-ray photoelectron spectroscopy (XPS) used in contemporary advanced materials research relies on a trustworthy binding energy (BE) referencing method. The C 1s peak corresponding to C-C/C-H bonds of adventitious carbon (AdC), present on a majority of air-exposed samples, is most commonly employed for this purpose, irrespective of whether samples are electrically conducting or not. Contrary to conventional practice, which takes the BE of C 1s peak of AdC as a constant, we find that the C 1s peak position E-B(F) varies over an alarmingly large range, from 284.08 to 286.74 eV, depending on the substrate, for nearly a hundred predominantly thin-film samples comprising metals, nitrides, carbides, borides, oxides, and oxynitrides. Our consistent measurements also show that, independent of materials system, E-B(F) of the C 1s peak is closely correlated to the sample work function phi(SA),such that the sum E-B(F) thorn /SA is constant, indicating that the electronic levels of the AdC layer align to the vacuum level, rather than to the Fermi level as commonly assumed. This phenomenon can be understood given that the AdC layer is not an inherent part of the analyzed sample and that the interaction to the substrate is weak, showing in that a common Fermi level is not established at the interface. Thus, a straightforward complementary measurement of /SA enables using the C 1s peak of AdC for the purpose of BE-scale calibration for samples exhibiting decent electrical conductivity. This new practice resolves problems associated with the conventional method and allows for more reliable bonding assignments. It is thus advisable that both ASTM and ISO XPS referencing guides relying on the use of AdC should be reviewed. (C) 2018 Elsevier B.V. All rights reserved.

    The full text will be freely available from 2020-04-27 17:09
  • 17.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Self-consistent modelling of X-ray photoelectron spectra from air-exposed polycrystalline TiN thin films2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 387, p. 294-300Article in journal (Refereed)
    Abstract [en]

    We present first self-consistent modelling of x-ray photoelectron spectroscopy (XPS) Ti 2p, N ls, 0 ls, and C ls core level spectra with a cross-peak quantitative agreement for a series of TiN thin films grown by dc magnetron sputtering and oxidized to different extent by varying the venting temperature Tv of the vacuum chamber before removing the deposited samples. So-obtained film series constitute a model case for XPS application studies, where certain degree of atmosphere exposure during sample transfer to the XPS instrument is unavoidable. The challenge is to extract information about surface chemistry without invoking destructive pre-cleaning with noble gas ions. All TiN surfaces are thus analyzed in the as-received state by XPS using monochromatic Al K alpha. radiation (hv = 1486.6 eV). Details of line shapes and relative peak areas obtained from deconvolution of the reference Ti 2p and N 1 s spectra representative of a native TiN surface serve as an input to model complex core level signals from air-exposed surfaces, where contributions from oxides and oxynitrides make the task very challenging considering the influence of the whole deposition process at hand. The essential part of the presented approach is that the deconvolution process is not only guided by the comparison to the reference binding energy values that often show large spread, but in order to increase reliability of the extracted chemical information the requirement for both qualitative and quantitative self-consistency between component peaks belonging to the same chemical species is imposed across all core-level spectra (including often neglected 0 is and C is signals). The relative ratios between contributions from different chemical species vary as a function of T-v presenting a self-consistency check for our model. We propose that the cross-peak self-consistency should be a prerequisite for reliable XPS peak modelling as it enhances credibility of obtained chemical information, while relying entirely on reference binding energy values introduces large ambiguity. (C) 2016 Elsevier B.V. All rights reserved.

  • 18.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Rhein Westfal TH Aachen, Germany.
    Mraz, S.
    Rhein Westfal TH Aachen, Germany.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schneider, J. M.
    Rhein Westfal TH Aachen, Germany.
    Unintentional carbide formation evidenced during high-vacuum magnetron sputtering of transition metal nitride thin films2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 385, p. 356-359Article in journal (Refereed)
    Abstract [en]

    Carbide signatures are ubiquitous in the surface analyses of industrially sputter-deposited transition metal nitride thin films grown with carbon-less source materials in typical high-vacuum systems. We use high-energy-resolution photoelectron spectroscopy to reveal details of carbon temporal chemical state evolution, from carbide formed during film growth to adventitious carbon adsorbed upon contact with air. Using in-situ grown Al capping layers that protect the as-deposited transition metal nitride surfaces from oxidation, it is shown that the carbide forms during film growth rather than as a result of post deposition atmosphere exposure. The XPS signature of carbides is masked by the presence of adventitious carbon contamination, appearing as soon as samples are exposed to atmosphere, and eventually disappears after one week-long storage in lab atmosphere. The concentration of carbon assigned to carbide species varies from 0.28 at% for ZrN sample, to 0.25 and 0.11 at% for TiN and HfN, respectively. These findings are relevant for numerous applications, as unintentionally formed impurity phases may dramatically alter catalytic activity, charge transport and mechanical properties by offsetting the onset of thermally induced phase transitions. Therefore, the chemical state of C impurities in PVD-grown films should be carefully investigated. (C) 2016 Elsevier B.V. All rights reserved.

  • 19.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Primetzhofer, D.
    Uppsala Univ, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Reference binding energies of transition metal carbides by core-level x-ray photoelectron spectroscopy free from Ar+ etching artefacts2018In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 436, p. 102-110Article in journal (Refereed)
    Abstract [en]

    We report x-ray photoelectron spectroscopy (XPS) core level binding energies (BEs) for the widely-applicable groups IVb-VIb transition metal carbides (TMCs) TiC, VC, CrC, ZrC, NbC, MoC, HfC, TaC, and WC. Thin film samples are grown in the same deposition system, by dc magnetron co-sputtering from graphite and respective elemental metal targets in Ar atmosphere. To remove surface contaminations resulting from exposure to air during sample transfer from the growth chamber into the XPS system, layers are either (i) Ar+ ion-etched or (ii) UHV-annealed in situ prior to XPS analyses. High resolution XPS spectra reveal that even gentle etching affects the shape of core level signals, as well as BE values, which are systematically offset by 0.2-0.5 eV towards lower BE. These destructive effects of Ar+ ion etch become more pronounced with increasing the metal atom mass due to an increasing carbon-to-metal sputter yield ratio. Systematic analysis reveals that for each row in the periodic table (3d, 4d, and 5d) C 1s BE increases from left to right indicative of a decreased charge transfer from TM to C atoms, hence bond weakening. Moreover, C 1s BE decreases linearly with increasing carbide/metal melting point ratio. Spectra reported here, acquired from a consistent set of samples in the same instrument, should serve as a reference for true deconvolution of complex XPS cases, including multinary carbides, nitrides, and carbonitrides. (C) 2017 Elsevier B.V. All rights reserved.

  • 20.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Primetzhofer, D.
    Uppsala University, Sweden.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Core-level spectra and binding energies of transition metal nitrides by non-destructive x-ray photoelectron spectroscopy through capping layers2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 396, p. 347-358Article in journal (Refereed)
    Abstract [en]

    We present the first measurements of x-ray photoelectron spectroscopy (XPS) core level binding energies (BE: s) for the widely-applicable group IVb-VIb polycrystalline transition metal nitrides (TMNs) TiN, VN, CrN, ZrN, NbN, MoN, HfN, TaN, and WN as well as AlN and SiN, which are common components in the TMN-based alloy systems. Nitride thin film samples were grown at 400.degrees C by reactive dc magnetron sputtering from elemental targets in Ar/ N-2 atmosphere. For XPS measurements, layers are either (i) Ar+ ion-etched to remove surface oxides resulting from the air exposure during sample transfer from the growth chamber into the XPS system, or (ii) in situ capped with a few nm thick Cr or W overlayers in the deposition system prior to air-exposure and loading into the XPS instrument. Film elemental composition and phase content is thoroughly characterized with time-of-flight elastic recoil detection analysis (ToF(-) ERDA), Rutherford backscattering spectrometry (RBS), and x-ray diffraction. High energy resolution core level XPS spectra acquired with monochromatic Al K alpha radiation on the ISO-calibrated instrument reveal that even mild etching conditions result in the formation of a nitrogen-deficient surface layer that substantially affects the extracted binding energy values. These spectra-modifying effects of Ar+ ion bombardment increase with increasing the metal atom mass due to an increasing nitrogen-to-metal sputter yield ratio. The superior quality of the XPS spectra obtained in a non-destructive way from capped TMN films is evident from that numerous metal peaks, including Ti 2p, V 2p, Zr 3d, and Hf 4f, exhibit pronounced satellite features, in agreement with previously published spectra from layers grown and analyzed in situ. In addition, the N/ metal concentration ratios are found to be 25-90% higher than those obtained from the corresponding ion-etched surfaces, and in most cases agree very well with the RBS and ToF-E ERDA values. The N 1 s BE: s extracted from capped TMN films, thus characteristic of a native surface, show a systematic trend, which contrasts with the large BE spread of literature "reference" values. Hence, non-destructive core level XPS employing capping layers provides an opportunity to obtain high-quality spectra, characteristic of virgin in situ grown and analyzed TMN films, although with larger versatility, and allows for extracting core level BE values that are more reliable than those obtained from sputter-cleaned N-deficient surfaces. Results presented here, recorded from a consistent set of binary TMNs grown under the same conditions and analyzed in the same instrument, provide a useful reference for future XPS studies of multinary materials systems allowing for true deconvolution of complex core level spectra. (C) 2016 Elsevier B. V. All rights reserved.

  • 21.
    Gurban, S.
    et al.
    Hungarian Academic Science, Hungary.
    Pecz, B.
    Hungarian Academic Science, Hungary.
    Menyhard, M.
    Hungarian Academic Science, Hungary.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Determination of the thickness distribution of a graphene layer grown on a 2 SiC wafer by means of Auger electron spectroscopy depth profiling2014In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 316, p. 301-307Article in journal (Refereed)
    Abstract [en]

    Auger electron spectroscopy (AES) depth profiling was applied for determination of the thickness of a macroscopic size graphene sheet grown on 2 in. 6H-SiC (0 0 0 1) by sublimation epitaxy. The measured depth profile deviated from the expected exponential form showing the presence of an additional, buffer layer. The measured depth profile was compared to the simulated one which allowed the derivation of the thicknesses of the graphene and buffer layers and the Si concentration of buffer layer. It has been shown that the graphene-like buffer layer contains about 30% unsaturated Si. The depth profiling was carried out in several points (diameter 50 mu m), which permitted the constructing of a thickness distribution characterizing the uniformity of the graphene sheet.

  • 22.
    Halim, Joseph
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Cook, Kevin M.
    Praxair Inc, NY 14150 USA.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Barsoum, Michel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel Univ, PA 19104 USA.
    XPS of cold pressed multilayered and freestanding delaminated 2D thin films of Mo2TiC2Tz and Mo2Ti2C3Tz (MXenes)2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 494, p. 1138-1147Article in journal (Refereed)
    Abstract [en]

    MXenes, transition metal carbides and/or nitrides, that are synthesized from the top down by etching of their 3D parent layered solids, the MAX phases, are the latest family of the two-dimensional solids discovered. When the A layers - mostly Al - are etched they are replaced by surface terminations, Tz mainly comprised of O-, OH- and F-terminations. One of the few techniques capable of quantifying these surface terminations is X-ray photo-electron spectroscopy, XPS. Herein, we undertook an XPS study of the out-of-plane ordered MXenes, Mo2TiC2Tz and Mo2Ti2C3Tz, in both multilayered, ML, cold pressed and delaminated thin film forms. The harsh conditions needed to etch these MAX phases into MLs, results in their partial oxidation. The hydroxide used to delaminate the MLs results in further oxidation and a reduction in the F-content. In all cases, etching resulted in a decrease in the Ti to Mo ratio implying that the former atoms are selectively etched. In all but the ML Mo2TiC2Tz case, the Mo to C ratio was also reduced. It follows that the loss of Ti also results in the loss of C atoms. Again with the exception of the ML Mo2Ti2C3Tz case, the number of termination moles per formula unit, z, was amp;gt; 2, which is energetically unfavorable and thus unlikely. However, if one assumes that not all of the O signal is coming from terminations but rather from O atoms that replace C atoms in the MX blocks, then z similar to 2. This work is an important step in quantifying and understanding the effects of etching on terminations and structure in these Mo and Ti-based MXenes.

  • 23.
    Halim, Joseph
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel University, PA 19104 USA; Drexel University, PA 19104 USA.
    Cook, Kevin M.
    Naval Air Syst Command, MD 20670 USA.
    Naguib, Michael
    Oak Ridge National Lab, TN 37831 USA.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Gogotsi, Yury
    Drexel University, PA 19104 USA; Drexel University, PA 19104 USA.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Barsoum, Michel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Department of Materials Science & Engineering, Drexel University, Philadelphia, PA 19104, USA.
    X-ray photoelectron spectroscopy of select multi-layered transition metal carbides (MXenes)2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 362, p. 406-417Article in journal (Refereed)
    Abstract [en]

    In this work, a detailed high resolution X-ray photoelectron spectroscopy (XPS) analysis is presented for select MXenes a recently discovered family of two-dimensional (2D) carbides and carbonitrides. Given their 2D nature, understanding their surface chemistry is paramount. Herein we identify and quantify the surface groups present before, and after, sputter-cleaning as well as freshly prepared vs. aged multi layered cold pressed discs. The nominal compositions of the MXenes studied here are Ti-3 C2Tx,Ti3CNTx, Nb2CTx and Nb4C3Tx where T represents surface groups that this work attempts to quantify. In all the cases, the presence of three surface terminations, O, OH and F, in addition to OH-terminations relatively strongly bonded to H2O molecules, was confirmed. From XPS peak fits, it was possible to establish the average sum of the negative charges of the terminations for the aforementioned MXenes. Based on this work, it is now possible to quantify the nature of the surface terminations. This information can, in turn, be used to better design and tailor these novel 2D materials for various applications. Published by Elsevier B.V.

  • 24. Hallstedt, J
    et al.
    Suvar, E
    Persson, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Wang, YB
    Radamson, HH
    Growth of high quality epitaxial Si1-x-yGexCy layers by using chemical vapor deposition2004In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 224, no 01-Apr, p. 46-50Article in journal (Refereed)
    Abstract [en]

    The epitaxial quality of non-selective and selective deposition of Si1-x-yGexCy (0 less than or equal to x less than or equal to 0.30, 0 less than or equal to y less than or equal to 0.02) layers has been optimized by using high-resolution reciprocal lattice mapping (HRRLM). The main goal was to incorporate a high amount of substitutional carbon atoms in Si or Si1-xGex matrix without creating defects. The carbon incorporation behavior was explained by chemical and kinetic effects of the reactant gases during epitaxial process. Although high quality epitaxial Si1-yCy layers can be deposited, lower electron mobility compared to Si layers was observed. (C) 2003 Elsevier B.V. All rights reserved.

  • 25.
    He, Jiangping
    et al.
    Linköping University, Department of Physics, Chemistry and Biology.
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Uhrberg, Roger
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Atomic structure of the carbon induced Si(001)c(4x4) surface2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, p. 5284-5287Article in journal (Refereed)
    Abstract [en]

       

  • 26.
    Hilfiker, James N.
    et al.
    JA Woollam Co Inc, NE 68508 USA.
    Hale, Jeffrey S.
    JA Woollam Co Inc, NE 68508 USA.
    Herzinger, Craig M.
    JA Woollam Co Inc, NE 68508 USA.
    Tiwald, Tom
    JA Woollam Co Inc, NE 68508 USA.
    Hong, Nina
    JA Woollam Co Inc, NE 68508 USA.
    Schoche, Stefan
    JA Woollam Co Inc, NE 68508 USA.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Estimating depolarization with the Jones matrix quality factor2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 494-499Article in journal (Refereed)
    Abstract [en]

    Mueller matrix (MM) measurements offer the ability to quantify the depolarization capability of a sample. Depolarization can be estimated using terms such as the depolarization index or the average degree of polarization. However, these calculations require measurement of the complete MM. We propose an alternate depolarization metric, termed the Jones matrix quality factor, QJM, which does not require the complete MM. This metric provides a measure of how close, in a least-squares sense, a Jones matrix can be found to the measured Mueller matrix. We demonstrate and compare the use of QJM to other traditional calculations of depolarization for both isotropic and anisotropic depolarizing samples; including nonuniform coatings, anisotropic crystal substrates, and beetle cuticles that exhibit both depolarization and circular diattenuation. (C) 2016 Elsevier B.V. All rights reserved.

  • 27.
    Hofmann, Tino
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of North Carolina Charlotte, NC 28223 USA; University of Nebraska, NE USA.
    Knight, S.
    University of Nebraska, NE USA.
    Sekora, D.
    University of Nebraska, NE USA.
    Schmidt, D.
    University of Nebraska, NE USA.
    Herzinger, C. M.
    JA Woollam Co Inc, NE 68508 USA.
    Woollam, J. A.
    JA Woollam Co Inc, NE 68508 USA.
    Schubert, E.
    University of Nebraska, NE USA.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska, NE USA.
    Screening effects in metal sculptured thin films studied with terahertz Mueller matrix ellipsometry2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 513-517Article in journal (Refereed)
    Abstract [en]

    The anisotropic optical dielectric functions of a metal (cobalt) slanted columnar thin film deposited by electronbeam glancing angle deposition are reported for the terahertz (THz) frequency domain before and after the slanted columnar thin film was passivated by a conformal alumina coating. A simple effective medium dielectric function homogenization approach which describes isolated, electrically conductive columns rendering the thin film biaxial (orthorhombic) is used to model the observed optical responses. Upon passivating the slanted columnar thin film with a 3 nm thick alumina film an increase of both the real and the imaginary part of the dielectric function for all major polarizability directions is found and attributed to screening effects within the spatially coherent metal nanocolumns. (C) 2016 Elsevier B.V. All rights reserved.

  • 28.
    Horvath, ZJ
    et al.
    Hungarian Acad Sci, Res Inst Tech Phys & Mat Sci, H-1525 Budapest 114, Hungary Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Järrendahl, Kenneth
    Linköping University, The Institute of Technology.
    Adam, M
    Hungarian Acad Sci, Res Inst Tech Phys & Mat Sci, H-1525 Budapest 114, Hungary Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Szabo, I
    Hungarian Acad Sci, Res Inst Tech Phys & Mat Sci, H-1525 Budapest 114, Hungary Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Van Tuyen, V
    Hungarian Acad Sci, Res Inst Tech Phys & Mat Sci, H-1525 Budapest 114, Hungary Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Czigany, Z
    Hungarian Acad Sci, Res Inst Tech Phys & Mat Sci, H-1525 Budapest 114, Hungary Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Electrical peculiarities in Al/Si/Ge/... /Ge/Si and Al/SiGe/Si structures2002In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 190, no 1-4, p. 403-407Article in journal (Refereed)
    Abstract [en]

    The current-voltage (I-V) and capacitance-voltage (C-V) behaviour of different Si/Ge multilayers and SiGe single layers prepared on p-type Si substrates by magnetron sputtering and annealing, has been studied in the temperature rang, of 80-320 K by using Al Schottky contacts as test structures. Although a significant influence of the microstructure of the Si/Ge multilayers and SiGe layers was obtained on the electrical behaviour of the structures, the structures exhibited similar specific features. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 29.
    Höglund, Linda
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Petrini, E.
    Acreo AB, Electrum 236, S-164 40 Kista, Sweden.
    Asplund, C.
    Acreo AB, Electrum 236, S-164 40 Kista, Sweden.
    Malm, H.
    Acreo AB, Electrum 236, S-164 40 Kista, Sweden.
    Andersson, J. Y.
    Acreo AB, Electrum 236, S-164 40 Kista, Sweden.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Optimising uniformity of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5525-5529Article in journal (Refereed)
    Abstract [en]

    A route towards optimisation of uniformity and density of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy (MOVPE) through successive variations of the growth parameters is reported. It is demonstrated that a key parameter in obtaining a high density of quantum dots is the V/III ratio, a fact which was shown to be valid when either AsH3 (arsine) or tertiary-butyl-arsine (TBA) were used as group V precursors. Once the optimum V/III ratio was found, the size distribution was further improved by adjusting the nominal thickness of deposited InAs material, resulting in an optimum thickness of 1.8 monolayers of InAs in our case. The number of coalesced dots was minimised by adjusting the growth interruption time to approximately 30 s. Further, the uniformity was improved by increasing the growth temperature from 485 °C to 520 °C. By combining these optimised parameters, i.e. a growth temperature of 520 °C, 1.8 monolayers InAs thickness, 30 s growth stop time and TBA as group V precursor, a full-width-half-maximum (FWHM) of the low temperature luminescence band of 40 meV was achieved, indicating a narrow dot size distribution.

  • 30. Johansson, M.
    et al.
    Ekedahl, Lars-Gunnar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Hydrogen adsorbed on palladium during water formation studied with palladium membranes2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 173, no 1-2, p. 122-133Article in journal (Refereed)
    Abstract [en]

    The amount of hydrogen adsorbed on palladium during water formation has been studied by measurements of the rate at which hydrogen permeates a palladium membrane. The water formation and hydrogen permeation rates were measured simultaneously for palladium membranes exposed to a hydrogen-oxygen-argon mixture on one side and to pure argon on the other side. Investigations were carried out for the temperatures 100, 150 and 200 °C at a total pressure of 760 Torr. If the rates are plotted as a function of a, where a = pH(2)/(pH(2)+pO(2)), pH(2) and pO(2) are the pressures of hydrogen and oxygen at the palladium surface, respectively, it is found that, at 100 °C, a peak occurs in the water formation rate at amax˜0.2. The palladium surface is dominated by hydrogen for a>amax and is hydrogen deficient for a>amax. This is consistent with a rate limiting step for the water forming reaction where adsorbed hydrogen is one of the reactants. It is also concluded that the heat of adsorption for hydrogen on the palladium surface is significantly lower than previously derived from experiments made under ultrahigh vacuum conditions.

  • 31. Johansson, M.
    et al.
    Ekedahl, Lars-Gunnar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    The water formation rate on platinum and palladium as a function of the surface hydrogen pressure from three-dimensional hydrogen pressure distributions2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 180, no 1-2, p. 27-35Article in journal (Refereed)
    Abstract [en]

    The water formation rate on platinum and palladium as a function of the reactant pressures at the catalytic surface has been determined from measurements of the three-dimensional hydrogen pressure distributions over the catalytic surface. Measurements were made for gas mixtures containing less than 1% of hydrogen and 20% of oxygen in argon at atmospheric pressure. The experiments were performed in a reactor with a simple and well-defined geometry which makes it possible to calculate the hydrogen pressure distribution in the entire region where measurements are made. The water formation rate as a function of the hydrogen pressure at the catalytic surface is obtained by comparing calculated hydrogen pressure distributions to measured ones. It is concluded that three-dimensional reactant pressure distributions can be used to accurately determine the reaction rate on a catalytic surface as a function of the reactant pressures at the surface. This is valuable for studies in the viscous pressure regime, where mass transfer limitations may be difficult to avoid. © 2001 Elsevier Science B.V.

  • 32.
    Jokubavicius, Valdas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yazdi, Gholamreza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan G.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Niu, Yuran
    Max Lab, Lund University.
    Zakharov, Alexei
    Max Lab, Lund University.
    Lakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Surface engineering of SiC via sublimation etching2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 390, p. 816-822Article in journal (Refereed)
    Abstract [en]

    We present a technique for etching of SiC which is based on sublimation and can be used to modify the morphology and reconstruction of silicon carbide surface for subsequent epitaxial growth of various materials, for example graphene. The sublimation etching of 6H-, 4H- and 3C-SiC was explored in vacuum (10−5 mbar) and Ar (700 mbar) ambient using two different etching arrangements which can be considered as Si-C and Si-C-Ta chemical systems exhibiting different vapor phase stoichiometry at a given temperature. The surfaces of different polytypes etched under similar conditions are compared and the etching mechanism is discussed with an emphasis on the role of tantalum as a carbon getter. To demonstrate applicability of such etching process graphene nanoribbons were grown on a 4H-SiC surface that was pre-patterned using the thermal etching technique presented in this study.

  • 33.
    Kakanakova-Georgieva, Anelia
    et al.
    Bulgarian Academy of Sciences, Sofia.
    Kassamakova, L
    Bulgarian Academy of Sciences, Plovdiv, Bulgaria.
    Marinova, Ts.
    Bulgarian Academy of Sciences, Sofia.
    Kakanakov, R.
    Bulgarian Academy of Sciences, Plovdiv, Bulgaria.
    Noblanc, O.
    Thomson-CSF/LCR, Orsay Cedex, France.
    Arnodo, C.
    Thomson-CSF/LCR, Orsay Cedex, France.
    Cassette, S.
    Thomson-CSF/LCR, Orsay Cedex, France.
    Brylinski, C.
    Thomson-CSF/LCR, Orsay Cedex, France.
    Interface chemistry of WN/4H-SiC structures1999In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 151, no 3-4, p. 225-232Article in journal (Refereed)
    Abstract [en]

    The interface chemistry of WN/4H–SiC structures has been studied by means of X-ray photoelectron spectroscopy (XPS). XPS investigations have been performed on as deposited, 800°C and 1200°C annealed (4 min) samples. The as deposited and 800°C annealed samples are characterized by chemically inert interfaces. Complete nitrogen out-diffusion from the WN layer, significant carbon diffusion into the contact layer, tungsten carbide and tungsten silicide formation occur during the 1200°C annealing process. The 800°C annealed WN/4H–SiC contacts are found to be of a Schottky type with a barrier height of 0.91 eV. The Schottky barrier height and the ideality factor show no significant changes during 100 h storage at 500°C under nitrogen and during operation at increasing temperature up to 350°C in air.

  • 34.
    Kakanakova-Georgieva, Anelia
    et al.
    Bulgarian Academy of Sciences, Sofia .
    Marinova, Ts.
    Bulgarian Academy of Sciences, Sofia .
    Noblanc, O.
    Thomson-CSF/LCR, Orsay Cedex, France.
    Arondo, C.
    Thomson-CSF/LCR, Orsay Cedex, France.
    Cassette, S.
    Thomson-CSF/LCR, Orsay Cedex, France.
    Brylinski, C.
    Thomson-CSF/LCR, Orsay Cedex, France.
    Interface chemistry of a Ti/ Au/ Pt/ Ti/ SiC structure1997In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 121/122, p. 208-212Article in journal (Refereed)
    Abstract [en]

    X-ray photoelectron spectroscopy (XPS) is used to investigate the chemical reactions and diffusion processes at Ti/Au/Pt/Ti/SiC interfaces for as deposited and annealed at 575°C for 10 min structures. The distribution of the elements and the change in their chemical state has been studied. The XP spectra indicate titanium carbide and platinum silicides formation at the SiC interface, which is preceded by the dissociation of SiC due to the reactivity of Ti at 575°C. TiC represents a barrier to the further diffusion of Ti to the SiC bulk and the Ti layer makes the diffusion of Pt into SiC difficult. The element distribution of the annealed structure demonstrates that Pt has diffused through almost the whole gold layer to the surface, an alloy of the two metals being formed.

  • 35.
    Kaushik, Priya Darshni
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Jamia Millia Islamia, India.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Lin, Pin-Cheng
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Kaur, Gurpreet
    University of Delhi, India.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Lakshmi, G. B. V. S.
    Interuniv Accelerator Centre, India.
    Avasthi, D. K.
    Interuniv Accelerator Centre, India; Amity Institute Nanotechnol, India.
    Gupta, Vinay
    University of Delhi, India.
    Aziz, Anver
    Jamia Millia Islamia, India.
    Siddiqui, Azher M.
    Jamia Millia Islamia, India.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yazdi, Gholamreza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Surface functionalization of epitaxial graphene on SiC by ion irradiation for gas sensing application2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 403, p. 707-716Article in journal (Refereed)
    Abstract [en]

    In this work, surface functionalization of epitaxial graphene grown on silicon carbide was performed by ion irradiation to investigate their gas sensing capabilities. Swift heavy ion irradiation using 100 MeV silver ions at four varying fluences was implemented on epitaxial graphene to investigate morphological and structural changes and their effects on the gas sensing capabilities of graphene. Sensing devices are expected as one of the first electronic applications using graphene and most of them use functionalized surfaces to tailor a certain function. In our case, we have studied irradiation as a tool to achieve functionalization. Morphological and structural changes on epitaxial graphene layers were investigated by atomic force microscopy, Raman spectroscopy, Raman mapping and reflectance mapping. The surface morphology of irradiated graphene layers showed graphene folding, hillocks, and formation of wrinkles at highest fluence (2 x 10(13) ions/cm(2)). Raman spectra analysis shows that the graphene defect density is increased with increasing fluence, while Raman mapping and reflectance mapping show that there is also a reduction of monolayer graphene coverage. The samples were investigated for ammonia and nitrogen dioxide gas sensing applications. Sensors fabricated on pristine and irradiated samples showed highest gas sensing response at an optimal fluence. Our work provides new pathways for introducing defects in controlled manner in epitaxial graphene, which can be used not only for gas sensing application but also for other applications, such as electrochemical, biosensing, magnetosensing and spintronic applications. (C) 2017 Elsevier B.V. All rights reserved.

  • 36.
    Keraudy, Julien
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Boyd, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Shimizu, Tetsuhide
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Tokyo Metropolitan Univ, Japan.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Jouan, P-Y
    Univ Nantes, France.
    Phase separation within NiSiN coatings during reactive HiPIMS discharges: A new pathway to grow NixSi nanocrystals composites at low temperature2018In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 454, p. 148-156Article in journal (Refereed)
    Abstract [en]

    The precise control of the growth nanostructured thin films at low temperature is critical for the continued development of microelectronic enabled devices. In this study, nanocomposite Ni-Si-N thin films were deposited at low temperature by reactive high-power impulse magnetron sputtering. A composite Ni-Si target (15 at.% Si) in combination with a Ar/N-2 plasma were used to deposit films onto Si(0 01) substrates, without any additional substrate heating or any post-annealing. The films microstructure changes from a polycrystalline to nanocomposite structure when the nitrogen content exceeds 16 at.%. X-ray diffraction and (scanning) transmission electron microscopy analyses reveal that the microstructure consists of nanocrystals, NixSi (x amp;gt; 1) 7-8 nm in size, embedded in an amorphous SiN x matrix. It is proposed that this nanostructure is formed at low temperatures due to the repeated-nucleation of NixSi nanocrystals, the growth of which is restricted by the formation of the SiNx phase. X-ray photoelectron spectroscopy revealed the trace presence of a ternary solid solution mainly induced by the diffusion of Ni into the SiNx matrix. Four-probe electrical measurements reveal all the deposited films are electrically conducing.

  • 37.
    Keraudy, Julien
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. IRT, France; University of Nantes, France.
    Ferrec, Axel
    University of Nantes, France.
    Richard-Plouet, Mireille
    University of Nantes, France.
    Hamon, Jonathan
    University of Nantes, France.
    Goullet, Antoine
    University of Nantes, France.
    Jouan, Pierre-Yves
    University of Nantes, France.
    Nitrogen doping on NiO by reactive magnetron sputtering: A new pathway to dynamically tune the optical and electrical properties2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 409, p. 77-84Article in journal (Refereed)
    Abstract [en]

    N-doped nickel oxide (NiO:N) thin films were deposited on glass and silicon substrates by reactive DC magnetron sputtering in Ar/O-2/N-2 gas atmosphere with a series of N-2/O-2 gas ratio ranging from 0 to 80%. X-ray diffraction measurements have revealed that the films are constituted of Ni1_xO grains and showed enhanced polycrystalline features with increasing N-doping concentration. For the first time, we report here that N-doping in the Ni-deficient NiO (Ni1-xO) film leads to a band-gap narrowing from 3.6 to 2.3 eV. X-ray photoelectron spectroscopy (XPS) measurements proved that up to 4 atomic percent (at.%) nitrogen can be incorporated at least at the surface of the NiO:N samples. In addition, XPS valence band spectra and UV-vis transmission measurements have demonstrated that the band-gap narrowing may originates from the contribution of an intermediate band (IB) similar to 2.4 eV just above the valence band maximum and the up-shifting of the valence band edge (similar to 0.3 eV) due to the introduction of occupied N 2p states. Local I-V measurements, carried out by conductive AFM (C-AFM), have revealed that the extrinsic doping of N atoms within the oxide can be a good way to precisely control the electrical conductivity of such p-type materials. (C) 2017 Elsevier B.V. All rights reserved.

  • 38.
    Khranovskyy, Volodymyr
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Surface morphology effects on the light-controlled wettability of ZnO nanostructures2012In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 258, no 20, p. 8146-8152Article in journal (Refereed)
    Abstract [en]

    ZnO nanostructures of diverse morphology with shapes of corrals and cabbages as well as open and filled hexagons and sheaves prepared by APMOCVD technique, are investigated with water contact angle (CA) analysis. The as-grown ZnO nanostructures exhibit pure hydrophobic behavior, which is enhanced with the increase of the nanostructures surface area. The most hydrophobic structures (CA = 124 degrees) were found to be the complex nanosheaf, containing both the macro-and nanoscale features. It is concluded that the nanoscale roughness contributes significantly to the hydrophobicity increase. The character of wettability was possible to switch from hydrophobic-to-superhydrophilic state upon ultra violet irradiation. Both the rate and amplitude of the contact angle depend on the characteristic size of nanostructure. The observed effect is explained due to the semiconductor properties of zinc oxide enhanced by increased surface chemistry effect in nanostructures.

  • 39.
    Khun, Kimleang
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Hussain Ibupoto, Zafar
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Chey, Chan Oeurn
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Comparative study of ZnO nanorods and thin films for chemical and biosensing applications and the development of ZnO nanorods based potentiometric strontium ion sensor2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 268, p. 37-43Article in journal (Refereed)
    Abstract [en]

    In this study, the comparative study of ZnO nanorods and ZnO thin films were performed regarding the chemical and biosensing properties and also ZnO nanorods based strontium ion sensor is proposed. ZnO nanorods were grown on gold coated glass substrates by the hydrothermal growth method and the ZnO thin films were deposited by electro deposition technique. ZnO nanorods and thin films were characterised by field emission electron microscopy [FESEM] and X-ray diffraction [XRD] techniques and this study has shown that the grown nanostructures are highly dense, uniform and exhibited good crystal quality. Moreover, transmission electron microscopy [TEM] was used to investigate the quality of ZnO thin film and we observed that ZnO thin film was comprised of nano clusters. ZnO nanorods and thin films were functionalised with selective strontium ionophore salicylaldehyde thiosemicarbazone [ST] membrane, galactose oxidase, and lactate oxidase for the detection of strontium ion, galactose and l-lactic acid, respectively. The electrochemical response of both ZnO nanorods and thin films sensor devices was measured by using the potentiometric method. The strontium ion sensor has exhibited good characteristics with a sensitivity of 28.65 +/- 0.52 mV/decade, for a wide range of concentrations from 1.00 x 10(-6) to 5.00 x 10(-2) M, selectivity, reproducibility, stability and fast response time of 10.00 s. The proposed strontium ion sensor was used as indicator electrode in the potentiometric titration of strontium ion versus ethylenediamine tetra acetic acid [EDTA]. This comparative study has shown that ZnO nanorods possessed better performance with high sensitivity and low limit of detection due to high surface area to volume ratio as compared to the flat surface of ZnO thin films.

  • 40.
    Lauridsen, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nedfors, N
    Uppsala University, Sweden .
    Jansson, U
    Uppsala University, Sweden .
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film 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.
    Ti-B-C nanocomposite coatings deposited by magnetron sputtering2012In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 258, no 24, p. 9907-9912Article in journal (Refereed)
    Abstract [en]

    Ti-B-C nanocomposite coatings with a B content of 8-17 at.% have been deposited by magnetron sputtering from B4C, Ti, and C targets. X-ray diffraction, photoelectron spectroscopy, and electron microscopy show that the coatings consist of nanocrystalline (nc) TiC: B embedded in a matrix of amorphous (a) C, BCx, TiOx and BOx. The fraction of amorphous phase scales with the Ti concentration, where the matrix predominantly consists of free C with some BCx in coatings with a C/Ti ratio andgt; 1, while the matrix predominantly consists of BCx with some free C in coatings with a C/Ti ratio andlt; 1. nc-TiC:B/a-BCx/a-C coatings with low amount of free C exhibit a contact resistance comparable to the contact resistance of an Ag sputtered coating at loads of similar to 1 N against an Au probe, despite the O content of similar to 16 at.%.

  • 41.
    Levin, Martina
    et al.
    Naphtenics Research AB Nynäs Petroleum.
    Wiklund, Per
    Naphtenics Research AB Nynäs Petroleum.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Adsorption and film growth of N-methylamino substituted triazoles on copper surfaces in dydrocarbon media2007In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 254, p. 1528-1533Article in journal (Refereed)
  • 42.
    Magnuson, Martin
    et al.
    Uppsala University.
    Butorin, Sergei M.
    Uppsala University.
    Werme, Lars
    Uppsala University.
    Nordgren, Joseph
    Uppsala University.
    Ivanov, Kirill E.
    RRC Kurchatov Institute, Moscow.
    Guo, Jinghua
    Lawrence Berkeley National Laboratory, Berkeley, USA.
    Shuh, David K.
    Lawrence Berkeley National Laboratory, Berkeley, USA.
    Uranium oxides investigated by X-ray absorption and emission spectroscopies2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 115, p. 5615-6518Article in journal (Refereed)
    Abstract [en]

    X-ray absorption and resonant X-ray emission measurements at the O 1s edge of the uranium oxides UO2, U3O8 and UO3 are presented. The spectral shapes of the O Kα X-ray emission spectra of UO3 exhibit significant excitation energy dependence, from an asymmetric to a symmetric form, which differs from those of UO2 and U3O8. This energy dependence is attributed to a significant difference in the oxygen–uranium hybridization between two different sites in the crystal structure of UO3. The spectral shapes of UO2 and U3O8 are also found to be different but without significant energy dependence. The experimental spectra of the valence and conduction bands of the uranium oxides are compared to the results of electronic structure calculations available in the literature.

  • 43.
    Magnuson, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Electronic Structure of ß-Ta Films from X-ray Photoelectron Spectroscopy and First-principles Calculations2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 470, p. 607-612Article in journal (Refereed)
    Abstract [en]

    The electronic structure and chemical bonding of ß-Ta synthesized as a thin 001-oriented film (space group P 21m) is investigated by 4f core level and valence band X-ray photoelectron spectroscopy and compared to α-Ta bulk. For the b-phase, the 4f7/2 peak is located at 21.91 eV and with the 4f5/2 at 23.81 eV which is 0.16 eV higher compared to the corresponding 4f peaks of the a-Ta reference. We suggest that this chemical shift originates from higher resistivity and tensile strain in the ß-Ta film. Furthermore, the 5d-5s states at the bottom of the valence band are shifted by 0.75 eV towards higher binding energy in ß-Ta compared to α-Ta. This is a consequence of the lower number of nearest neighbors with four in ß-Ta compared to eight in the α-Ta phase. The difference in the electronic structures, spectral line shapes of the valence band and the energy positions of the Ta 4f, 5p core-levels of b-Ta versus a-Ta are discussed in relation to calculated states of ß-Ta and α-Ta. In particular, the lower number of states at the Fermi level of ß-Ta (0.557 states/eV/atom) versus α-Ta (1.032 states/eV/atom) that according to Mott’s law should decrease the conductivity in metals and affect the stability by charge redistribution in the valence band. This is experimentally supported from resistivity measurements of the film yielding a value of ~170 µW cm in comparison to α-Ta bulk with a reported value of ~13.1 µW cm.

  • 44.
    Malysheva, Liubov
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Onipko, A
    Valiokas, Ramunas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    First-principles modeling of oligo(ethylene glycol)-terminated and amide group containing alkanethiolates2005In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 246, no 4, p. 372-376Article in journal (Refereed)
    Abstract [en]

    Recently, self-assemblies of HS(CH2)(15)CONH(CH2CH2O)(6)H were found to undergo a reversible temperature-driven conformational transition from the helical to all-trans state [R. Valiokas, M. Ostblom, S. Svedhem, S.C.T. Svensson, B. Liedberg 104 (2000) 7565]. The transition reveals distinctive signatures in the reflection-absorption (RA) spectrum associated with different conformations of the OEG portion of the SAM [R. Valiokas, M. Ostblom, S. Svedhem, S.C.T. Svensson, B. Liedberg 104 (2000) 7565]. Here we report an extensive ab initio modeling of infrared RA spectra of molecular constituents of OEG-terminated amide-containing SAMs. The model spectra for this type of molecules (with large OEG and alkyl portions) are obtained, for the first time, by using DFT methods with gradient corrections. The position and relative intensities of all characteristic bands, observed in the fingerprint region of the SAM RA spectrum, are shown to be well reproduced by the single-molecule model spectrum calculated for a certain relative orientation of the alkyl- and OEG portions and the amide bridge. This provides us additional information about actual structure, particularly, molecular orientation within the OEG-containing SAMs in focus. (c) 2004 Elsevier B.V. All rights reserved.

  • 45.
    Marinova, Ts.
    et al.
    Bulgarian Academy of Sciences, Sofia.
    Kakanakova-Georgieva, Anelia
    Bulgarian Academy of Sciences, Sofia.
    Kalitzova, M.
    Bulgarian Academy of Sciences, Sofia.
    Vitali, G.
    Universita ‘‘La Sapienza'', Rome.
    Pizzuto, C.
    Universita ‘‘La Sapienza'', Rome.
    Zollo, G.
    Universita ‘‘La Sapienza'', Rome.
    XPS depth profiling of laser-annealed Zn+-implanted GaAs1997In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 109/110, p. 80-86Article in journal (Refereed)
    Abstract [en]

    Data on the effects of 140 keV Zn+-implantation in (100) GaAs and the consequent low power pulsed laser annealing (LPPLA) on the As/Ga ratio and the chemical states of the elements at the surface and in the subsurface region are presented. The results include the depth distribution of the elements for virgin, as-implanted and implanted+LPPLA [30×(4.5/7.5) MW/cm2] samples. The X-ray photoelectron spectra of as-implanted samples show that a low-intensity Zn 2p peak is observed after 20 min of Ar+ sputtering with an energy of 3 keV, corresponding to about 20 nm of etched material. The depth profiling XPS analysis confirms the ‘recovering' of the stoichiometry of Zn+-implanted specimens after LPPLA with laser pulses of a power density in the energy window of (5–7 MW/cm2). At laser pulse power densities outside of this energy window (4.5 and 7.5 MW/cm2) Zn appears again in the XP spectra after 20 min sputtering as in the case of as-implanted GaAs.

  • 46.
    Mock, Alyssa
    et al.
    University of Nebraska Lincoln, NE USA.
    Carlson, Timothy
    University of Nebraska Lincoln, NE USA.
    VanDerslice, Jeremy
    University of Nebraska Lincoln, NE USA; JA Woollam Co Inc, NE USA.
    Mohrmann, Joel
    JA Woollam Co Inc, NE USA.
    Woollam, John A.
    University of Nebraska Lincoln, NE 68588 USA; JA Woollam Co Inc, NE USA.
    Schubert, Eva
    University of Nebraska Lincoln, NE USA.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska Lincoln, NE USA; Leibniz Institute Polymer Research Dresden, Germany.
    Multiple-layered effective medium approximation approach to modeling environmental effects on alumina passivated highly porous silicon nanostructured thin films measured by in-situ Mueller matrix ellipsometry2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 663-666Article in journal (Refereed)
    Abstract [en]

    Optical changes in alumina passivated highly porous silicon slanted columnar thin films during controlled exposure to toluene vapor are reported. Electron-beam evaporation glancing angle deposition and subsequent atomic layer deposition are utilized to deposit alumina passivated nanostructured porous silicon thin films. In-situ Mueller matrix generalized spectroscopic ellipsometry in an environmental cell is then used to determine changes in optical properties of the nanostructured thin films by inspection of individual Mueller matrix elements, each of which exhibit sensitivity to adsorption. The use of a multiple-layered effective medium approximation model allows for accurate description of the inhomogeneous nature of toluene adsorption onto alumina passivated highly porous silicon slanted columnar thin films. (C) 2016 Elsevier B.V. All rights reserved.

  • 47.
    Nilsson, H.-E.
    et al.
    Department of Information Technology, Mid-Sweden University, S-851 70 Sundsvall, Sweden.
    Martinez, A.
    Department of Electronics, Kungl. Tekniska Högskolan, Electrum 229, S-164 40 Kista, Sweden.
    Sannemo, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Numerical study of Bloch electron dynamics in wide band-gap semiconductors2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 184, no 1-4, p. 199-203Article in journal (Refereed)
    Abstract [en]

    In this paper, we are using numerical calculations to demonstrate the importance of band to band tunneling in wide band-gap semiconductors. We have considered 4H-SiC, 3C-SiC and wurtzite GaN as prototype semiconductors in the demonstration. Wide band-gap semiconductors allow device operation under very high-applied electric fields, where significant band to band tunneling is expected to occur. Hexagonal wide band-gap semiconductors have a valence band structure with a large number of bands separated by rather small energies. Our calculation shows that this leads to a very significant band to band tunneling even at relatively low electric fields. In cubic wide band-gap semiconductors the tunneling is much less pronounced. However, at the valence band maximum the band separations are small enough to allow significant band to band tunneling. The spin-orbit interaction tends to bend the band near the maximum creating degradation from a parabolic curvature. This bending is found to significantly influence the band to band tunneling process. © 2001 Elsevier Science B.V. All rights reserved.

  • 48.
    Nilsson, Sara
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Uppsala University, Sweden .
    Robinson, Nathaniel D.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Electrochemical quartz crystal microbalance study of polyelectrolyte film growth under anodic conditions2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 280, p. 783-790Article in journal (Refereed)
    Abstract [en]

    Coating hard materials such as Pt with soft polymers like poly-l-lysine is a well-established technique for increasing electrode biocompatibility. We have combined quartz crystal microgravimetry with dissipation with electrochemistry (EQCM-D) to study the deposition of PLL onto Pt electrodes under anodic potentials. Our results confirm the change in film growth over time previously reported by others. However, the dissipation data suggest that, after the short initial phase of the process, the rigidity of the film increases with time, rather than decreasing, as previously proposed. In addition to these results, we discuss how gas evolution from water electrolysis and Pt etching in electrolytes containing Cl affect EQCM-D measurements, how to recognize these effects, and how to reduce them. Despite the challenges of using Pt as an anode in this system, we demonstrate that the various electrochemical processes can be understood and that PLL coatings can be successfully electrodeposited.

  • 49. Petersson, L.-G.
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Fogelberg, J.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Oxygen as a poison or promoter in the catalytic dissociation of H2, C2H2, C2H4, and NH3 on palladium1986In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 27, p. 275-Article in journal (Refereed)
    Abstract [en]

    The dissociation rates of H2, C2H4, C2H4, and NH3 have been studied on oxygen covered Pd surfaces by measuring the water desorption rates during exposure to each of the molecules. These results are correlated with the hydrogen response of a Pd-MOS structure. The measurements show a trend (at 473 K) where oxygen blocks H2 dissociation, blocks C2H4 dissociation only above a certain oxygen coverage, has no influence on C2H2 dissociation, and promotes NH3 dissociation.

  • 50.
    Rice, Charles
    et al.
    University of Nebraska, NE USA.
    Mock, Alyssa
    University of Nebraska, NE USA.
    Sekora, Derek
    University of Nebraska, NE USA.
    Schmidt, Daniel
    University of Nebraska, NE USA.
    Hofmann, Tino
    University of Nebraska, NE USA.
    Schubert, Eva
    University of Nebraska, NE USA.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska, NE 68588 USA; University of Nebraska, NE USA; Leibniz Polymer Research Institute, Germany.
    Control of slanting angle, porosity, and anisotropic optical constants of slanted columnar thin films via in situ nucleation layer tailoring2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 766-771Article in journal (Refereed)
    Abstract [en]

    Electron-beam evaporation at a glancing angle of 85 is utilized to fabricate highly ordered, spatially coherent titanium slanted columnar thin films. Prior to deposition of the slanted columnar thin films, a titanium nucleation layer is deposited using electron-beam deposition at normal incidence with various intended nucleation layer thicknesses of 0 nm, 5 nm, 7.5 nm, 10 nm, 20 nm, and 50 nm. Structural and optical properties of the anisotropic porous thin films are studied by scanning electron microscopy, atomic force microscopy, and Mueller matrix generalized spectroscopic ellipsometry in the near infrared to ultra-violet spectral regions. An anisotropic effective medium approximation is employed for analysis of the ellipsometry data in order to determine slanting angle and porosity model parameters. We find that the slanting angle and titanium volume fraction are strongly influenced by the nucleation layer thickness. Structural parameters of SCTFs deposited on 50 nm nucleation layers are similar to those from SCTFs with no nucleation layer. For small nucleation layer thicknesses, the corresponding SCTF slanting angle and titanium volume fraction decrease reaching a minimum of approximate to 33 degrees and approximate to 12% respectively, at 10 nm nucleation layer thickness. In accordance with the strong decrease in volume fraction we observe substantial reduction of the effective anisotropic thin film optical constants. We find the slanting angle and porosity variation reproducible and suggest use of a nucleation layer for control of slanting angle and porosity of slanted columnar thin films. (C) 2017 Published by Elsevier B.V.

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