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  • 1. Alarco, J A
    et al.
    Brorsson, G
    Olin, Håkan
    Department of Physics, Chalmers University of Technology/University of Göteborg.
    Olsson, E
    Early stages of growth of YBa2Cu3O7− high Tc superconducting films on (001) Y-ZrO2 substrates1994Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 75, s. 3202-3204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Theearly stages of growth of high quality YBa2Cu3O7− (YBCO) filmsgrown on (001) Y-ZrO2 (YSZ) substrates by pulsed laser depositionhave been studied using a combination of atomic force microscopyand transmission electron microscopy. A one unit cell thick YBCOlayer and relatively large CuO particles formed in the initialstages. Additional YBCO grew on top of the first layerin the form of one or a few unit cellhigh c-axis oriented islands about 30 nm in diameter. Therounded islands subsequently coalesced into faceted domains. Elongated Y2BaCuO5 particlesnucleated after the first layer of YBCO. A highly texturedBaZrO3 layer formed between the YSZ and the YBCO witha cube-on-cube dominant orientation relationship with respect to the YBCOfilm. Journal of Applied Physics is copyrighted by The American Institute of Physics.

  • 2. Bellotti, E.
    et al.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Brennan, K.F.
    Ruden, P.P.
    Trew, R.
    Monte Carlo calculation of hole initiated impact ionization in 4H phase SiC2000Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 87, nr 8, s. 3864-3871Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, we present a comprehensive, full band theoretical study of the high field, hole transport properties of the 4H phase of silicon carbide (4H-SiC). The calculations are performed using a full band ensemble Monte Carlo simulation that includes numerically tabulated impact ionization rates, and phonon and ionized impurity scattering rates. In addition, the simulation includes a mechanism, interband tunneling, by which the holes can move between bands in the proximity of band intersection points, It is found that there exists a significant anisotropy in the calculated steady-state hole drift velocity for fields applied parallel and perpendicular to the c-axis direction. Good agreement with experimental measurements of the hole initiated impact ionization coefficient for fields applied along the c axis is obtained, provided that interband tunneling in the proximity of band intersections is included in the model. If interband tunneling is not included, the calculated ionization coefficients are orders of magnitude lower than the experimental measurements. © 2000 American Institute of Physics.

  • 3.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    Kaplan, AFH
    Powell, J
    The absorption of light by rough metal surfaces - a three-dimensional ray-tracing analysis2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 10, s. 103515-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The laser absorptance of rough surfaces has been investigated by using Monte Carlo simulations based on three-dimensional (3D) ray tracing. The influence of multiple scattering, shadowing, and the Fresnel-equation based angle dependence is discussed. The 3D results are compared to previously published results from a two-dimensional ray-tracing analysis and the different applications of the two models are explained.

  • 4.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Powell, J.
    Kaplan, A. F. H.
    A ray-tracing analysis of the absorption of light by smooth and rough metal surfaces2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 11, artikel-id 113504Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ray tracing has been employed to investigate the absorption of light by smooth and random rough metal surfaces. For normally incident light the absorptance of the surface increases with surface roughness. However, for light incident at a tangent to the surface the absorptance-surface roughness relationship is more complex. For example, in certain cases the absorptance can rise, fall, and rise again as the surface roughness increases. In this paper this complex absorptance-roughness relationship is defined and explained. The wavelengths of the light chosen for this study correspond to the primary and secondary output wavelengths of Nd:YAG lasers.

  • 5.
    Höglund, C.
    et al.
    European Spallat Source ESS AB, SE-22100 Lund, Sweden.
    Alling, B.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden.
    Jensen, J.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden.
    Hultman, L.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden.
    Birch, J.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden.
    Hall-Wilton, Richard
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion. European Spallat Source ESS AB, SE-22100 Lund, Sweden.
    Growth and oxidization stability of cubic Zr1-xGdxN solid solution thin films2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, nr 19, artikel-id 195301Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report Zr1-xGdxN thin films deposited by magnetron sputter deposition. We show a solid solubility of the highly neutron absorbing GdN into ZrN along the whole compositional range, which is in excellent agreement with our recent predictions by first-principles calculations. An oxidization study in air shows that Zr1-xGdxN with x reaching from 1 to close to 0 fully oxidizes, but that the oxidization is slowed down by an increased amount of ZrN or stopped by applying a capping layer of ZrN. The crystalline quality of Zr0.5Gd0.5N films increases with substrate temperatures increasing from 100 degrees C to 900 degrees C. (C) 2015 Author(s).

  • 6.
    Li, Jiantong
    et al.
    School of Information and Communication, Royal Institute of Technology.
    Unander, Tomas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Cabezas, Ana López
    School of Information and Communication, Royal Institute of Technology.
    Shao, Botao
    School of Information and Communication, Royal Institute of Technology.
    Liu, Zhiying
    Solid-State Electronics, The Ångström Laboratory, Uppsala University.
    Feng, Yi
    School of Information and Communication, Royal Institute of Technology.
    Forsberg, Esteban Bernales
    School of Information and Communication, Royal Institute of Technology.
    Zhang, Zhi-Bin
    School of Information and Communication, Royal Institute of Technology.
    Jõgi, Indrek
    Materials Chemistry, The Ångström Laboratory, Uppsala University.
    Gao, Xindong
    Solid-State Electronics, The Ångström Laboratory, Uppsala University.
    Boman, Mats
    Materials Chemistry, The Ångström Laboratory, Uppsala University.
    Zheng, Li-Rong
    School of Information and Communication, Royal Institute of Technology.
    Östling, Mikael
    School of Information and Communication, Royal Institute of Technology.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Zhang, Shi-Li
    School of Information and Communication, Royal Institute of Technology.
    Ink-Jet Printed Thin-Film Transistors with Carbon Nanotube Channels Shaped in Long Strips2011Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, nr 8, s. Art. no. 084915-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work reports on the development of a class of sophisticated thin-film transistors (TFTs) based on ink-jet printing of pristine single-walled carbon nanotubes (SWCNTs) for the channel formation. The transistors are manufactured on oxidized silicon wafers and flexible plastic substrates at ambient conditions. For this purpose, ink-jet printing techniques are developed with the aim of high-throughput production of SWCNT thin-film channels shaped in long strips. Stable SWCNT inks with proper fluidic characteristics are formulated by polymer addition. The present work unveils, through Monte Carlo simulations and in light of heterogeneous percolation, the underlying physics of the superiority of long-strip channels for SWCNT TFTs. It further predicts the compatibility of such a channel structure with ink-jet printing, taking into account the minimum dimensions achievable by commercially available printers. The printed devices exhibit improved electrical performance and scalability as compared to previously reported ink-jet printed SWCNT TFTs. The present work demonstrates that ink-jet printed SWCNT TFTs of long-strip channels are promising building blocks for flexible electronics. (C) 2011 American Institute of Physics. [doi:10.1063/1.3569842]

  • 7.
    Massey, M. K.
    et al.
    Durham University, United Kingdom.
    Kotsialos, A.
    Durham University, United Kingdom.
    Qaiser, F.
    Durham University, United Kingdom.
    Zeze, D. A.
    Durham University, United Kingdom.
    Pearson, C.
    Durham University, United Kingdom.
    Volpati, Diogo
    University of São Paulo-USP, Brazil; Durham University, United Kingdom.
    Bowen, L.
    Durham University, United Kingdom.
    Pettyl, M. C.
    Durham University, United Kingdom.
    Computing with carbon nanotubes: Optimization of threshold logic gates using disordered nanotube/polymer composites2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, nr 13, artikel-id 134903Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper explores the use of single-walled carbon nanotube (SWCNT)/poly(butyl methacrylate) composites as a material for use in unconventional computing. The mechanical and electrical properties of the materials are investigated. The resulting data reveal a correlation between the SWCNT concentration/viscosity/conductivity and the computational capability of the composite. The viscosity increases significantly with the addition of SWCNTs to the polymer, mechanically reinforcing the host material and changing the electrical properties of the composite. The electrical conduction is found to depend strongly on the nanotube concentration; Poole-Frenkel conduction appears to dominate the conductivity at very low concentrations (0.11% by weight). The viscosity and conductivity both show a threshold point around 1% SWCNT concentration; this value is shown to be related to the computational performance of the material. A simple optimization of threshold logic gates shows that satisfactory computation is only achieved above a SWCNT concentration of 1%. In addition, there is some evidence that further above this threshold the computational efficiency begins to decrease. (C) 2015 AIP Publishing LLC.

  • 8.
    Nilsson, Hans-Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Englund, U
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Hjelm, Mats
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Belotti, E
    Brennan, K
    Full band Monte Carlo study of high field transport in cubic phase silicon carbide2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, nr 6, s. 3389-3394Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A full band Monte Carlo study of the electron transport in 3C-SiC is presented based on an ab initio band structure calculation using the local density approximation to the density functional theory. The scattering rates and impact ionization transition rates have been calculated numerically from the ab initio band structure using both energy dispersion and numerical wave functions. This approach reduces the number of empirical parameters needed to a minimum. The two empirical coupling constants used have been deduced by fitting the simulated mobility as a function of lattice temperature to experimental data. The peak velocity was found to be approximately 2.2*107 cm/s with a clear negative differential mobility above 600 kV/cm. The electron initiated impact ionization coefficients were found to be 2-10 times stronger than the reported values for the hole initiated impact ionization

  • 9.
    Nilsson, Hans-Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Hjelm, Mats
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Fröjdh, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Persson, Clas
    Sannemo, Ulf
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Full band Monte Carlo simulation of electron transport in 6H-SiC1999Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 86, nr 2, s. 965-973Artikel i tidskrift (Refereegranskat)
  • 10.
    Nilsson, Hans-Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Martinez, A.
    Ghillino, E.
    Sannemo, U.
    Bellotti, E.
    Goano, M.
    Numerical modeling of hole interband tunneling in wurtzite GaN and SiC2001Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, nr 6, s. 2847-2852Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The time evolution of Bloch electrons (holes) moving in a constant electric field has been studied for GaN and 2H-SiC using a numerical model based on realistic band structures. The large band gap of GaN and the SiC polytypes provide much larger critical fields than in conventional semiconductors, which allows device operation at very high electric fields. At sufficiently high electric fields the carriers may change band during drift due to tunneling. GaN has a direct band gap, while the hexagonal SiC polytypes have indirect band gaps. In spite of this difference the valence band structure is very similar due to the wurtzite symmetry. In this work the GaN and the 2H-SiC polytype are considered as wurtzite prototype semiconductors in order to study valence band to band tunneling in wurtzite semiconductors for electric fields directed along the c axis. A large valence band to band tunneling probability was found for both materials at electric fields above 400 kV/cm. This shows the importance of considering band to band tunneling in studies of high field hole transport in wide band-gap hexagonal semiconductor materials. The proposed numerical approach can be used to enhance the interband tunneling models used in Monte Carlo simulation of carrier transport in hexagonal semiconductors.

  • 11.
    Nilsson, Hans-Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Sannemo, U.
    Petersson, Sture
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Monte carlo simulation of electron transport in 4H-SiC using a two band model with multiple minima1996Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 80, nr 6, s. 3365-3369Artikel i tidskrift (Refereegranskat)
  • 12. Persson, C
    et al.
    Lindefelt, Ulf
    Department of Physics and Measurement Technology, Linköping University, S-581 83 Linköping, Sweden .
    Sernelius, B.G.
    Band gap narrowing in n-type 3C-, 2H-, 4H-, 6H-SiC and Si1999Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 86, s. 4419-Artikel i tidskrift (Refereegranskat)
  • 13. Ruden, P.P.
    et al.
    Bellotti, E.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Brennan, K.F.
    Modeling of Band-to-band tunneling transitions during drift in Monte Carlo transport simulations2000Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 88, nr 3, s. 1488-1493Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The conventional method of semiconductor charge carrier transport investigations using full band ensemble Monte Carlo simulations is extended to allow for tunneling between bands during accelerated drift of the carriers. The essentially classical picture of transport, as simulated, is preserved by implementing a stochastic selection of the band index of the initial state of each scattering process associated with phonons, with impurities, or with impact ionization. Relative probabilities for the band assignment are calculated from the overlap integrals of the cell-periodic parts of Bloch wave functions belonging to different bands, for k-vectors along the carrier k-space trajectory between successive scattering events. As an example, the method is applied to Monte Carlo transport simulations for holes in 4H SiC in a homogeneous applied electric field. Tunneling between valence bands during the drift phases is shown to have a significant impact on the carrier energy distributions when large electric fields are applied, and on physical parameters that directly depend on the carrier energy, such as the hole initiated impact ionization coefficient.

  • 14.
    Salmi, Ari
    et al.
    VTT Tech Res Ctr Finland, Espoo, Finland.
    Salminen, Lauri I.
    VTT Tech Res Ctr Finland, Espoo, Finland.
    Engberg, Birgitta A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Bjorkqvist, Tomas
    Tampere Univ Tech, Dept Automat Sci & Eng, Tampere, Finland.
    Haeggstrom, Edward
    Univ Helsinki, Elect Res Lab, Dept Phys, Div Mat Phys, Helsinki, Finland.
    Repetitive impact loading causes local plastic deformation in wood2012Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, nr 2, s. Art. no. 024901-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The relationship between the impactor velocity and the amount of strain localization in a single impact compression of cellular solids is known. However, few studies report on the effects of repeated high frequency compression. We therefore studied the mechanical behavior of Norway spruce, a cellular viscoelastic material, before, during, and after cyclic high frequency, high strain rate, compression. A custom made device applied 5000-20 000 unipolar (constrained compression and free relaxation) fatigue cycles with a 0.75 mm peak-to-peak amplitude at 500 Hz frequency. The consequences of this treatment were quantified by pitch-catch ultrasonic measurements and by dynamic material testing using an encapsulated Split-Hopkinson device that incorporated a high-speed camera. The ultrasonic measurements quantified a stiffness modulus drop and revealed the presence of a fatigued low modulus layer near the impacting surface. Such a localized plastic deformation is not predicted by classical mechanics. We introduce a simple model that explains several changes in the mechanical properties caused by fatiguing. The high speed images indicated pronounced strain localization in the weakest (thinnest walls) parts of the earlywood layers, and revealed strain propagation as a function of time. We present a hypothesis explaining why there is a fatigued layer formed in a piece of wood that has sustained cyclic compression and free relaxation. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3676206]

  • 15.
    Volpati, D.
    et al.
    Durham university, UK.
    Massey, M. K.
    Durham university, UK.
    Johnson, D. W.
    Durham university, UK.
    Kotsialos, A.
    Durham university, UK.
    Qaiser, F.
    Durham university, UK.
    Pearson, C.
    Durham university, UK.
    Coleman, K. S.
    Durham university, UK.
    Tiburzi, G.
    Durham university, UK.
    Zeze, D. A.
    Durham university, UK.
    Petty, M. C.
    Durham university, UK.
    Exploring the alignment of carbon nanotubes dispersed in a liquid crystal matrix using coplanar electrodes2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, nr 12, artikel-id 125303Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the use of a liquid crystalline host medium to align single-walled carbon nanotubes in an electric field using an in-plane electrode configuration. Electron microscopy reveals that the nanotubes orient in the field with a resulting increase in the DC conductivity in the field direction. Current versus voltage measurements on the composite show a nonlinear behavior, which was modelled by using single-carrier space-charge injection. The possibility of manipulating the conductivity pathways in the same sample by applying the electrical field in different (in-plane) directions has also been demonstrated. Raman spectroscopy indicates that there is an interaction between the nanotubes and the host liquid crystal molecules that goes beyond that of simple physical mixing.

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