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  • 1.
    Al-Hamadandy, Raied
    et al.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Goss, J.P.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Briddon, P.R.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Mojarad, Shahin A.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Al-Hadidi, Meaad
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    O'Neill, A.G.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Oxygen vacancy migration in compressively strained SrTiO32013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The intrinsic properties of strontium titanate render it promising in applications such as gate dielectrics and capacitors. However, there is growing evidence that oxygen vacancies significantly impact upon its use, with the diffusion and deep donor level of the oxygen vacancy leading to electrical leakage. Where grown epitaxially on a lattice mismatched substrate, SrTiO 3 undergoes bi-axial strain, altering its crystal structure and electronic properties. In this paper, we present the results of first-principles simulations to evaluate the impact of strain in a (001) plane upon the migration of oxygen vacancies. We show that in the range of strains consistent with common substrate materials, diffusion energies in different directions are significantly affected, and for high values of strain may be altered by as much as a factor of two. The resulting diffusion anisotropy is expected to impact upon the rate at which oxygen vacancies are injected into the films under bias, a critical factor in the leakage and resistive switching seen in this material

  • 2.
    Al-Hamadany, R.
    et al.
    Newcastle University.
    Goss, J.P.
    Newcastle University.
    Briddon, P.R.
    Newcastle University.
    Mojarad, S.A.
    Newcastle University.
    O'Neill, A.G.
    Newcastle University.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Impact of tensile strain on the oxygen vacancy migration in SrTiO3: Density functional theory calculations2013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Strontium titanate is a promising dielectric material for device applications including capacitors and gate dielectrics. However, oxygen vacancies, which are inevitable donor defects mobile under bias at room temperature, lead to undesirable leakage current in SrTiO3 thin films. Epitaxially grown SrTiO3 on lattice mismatched substrates leads to strained SrTiO3, inducing structural phase transitions from a cubosymmetric non-ferroelectric geometry to tetragonal and orthorhombic structures, depending upon the sign of the strain. In this study, density functional calculations have been performed to determine the impact of isotropic biaxial tensile strain in a (001) plane upon the phase of SrTiO3 and the activation energy for the migration of oxygen vacancies in such strained SrTiO3. The phase transition of the host material yields anisotropy in oxygen vacancy diffusion for diffusion within and between planes parallel to the strain. We found a general reduction in the barrier for diffusion within and normal to the plane of tensile strain. The inter-plane diffusion barrier reduces up to 25% at high values of strain. The variation in the barrier corresponding to in-plane diffusion is smaller in comparison to inter-plane diffusion. Finally, we reflect upon how the interplay between lattice strain with native defects plays a crucial role in the conduction mechanism of thin film, strained SrTiO3

  • 3.
    Almer, J.
    et al.
    Advanced Photon Source (APS), Argonne National Laboratory, Argonne.
    Lienert, U.
    Advanced Photon Source (APS), Argonne National Laboratory, Argonne.
    Peng, R.L.
    Linköping universitet.
    Schlauer, C.
    Linköping universitet.
    Odén, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Strain and texture analysis of coatings using high-energy x-rays2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 94, nr 1, s. 697-702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the internal strain and crystallographic orientation (texture) in physical-vapor deposited metal nitride coatings of TiN and CrN. A high-energy diffraction technique is presented that uses synchrotron x rays and an area detector, and which allows the strain and intensity distributions of multiple crystallographic planes to be measured by a single x-ray exposure. Unique texture states and nonlinear sin2 strain distributions are observed for all coatings investigated. Quantitative analysis indicates that existing micromechanical models can reasonably predict strain and corresponding stress for mixed-hkl reflections but are inadequate for fully describing measured data. Alternative mechanisms involving deposition-induced defects are proposed

  • 4.
    Ashwin, M.J.
    et al.
    Interdisciplinary Research Centre for Semiconductor Materials, The Blackett Laboratory, Imperial College of Science, Technology and Medicine, London.
    Pritchard, R.E.
    Interdisciplinary Research Centre for Semiconductor Materials, The Blackett Laboratory, Imperial College of Science, Technology and Medicine, London.
    Newman, R.C.
    Interdisciplinary Research Centre for Semiconductor Materials, The Blackett Laboratory, Imperial College of Science, Technology and Medicine, London.
    Joyce, T.B.
    Department of Materials Science and Engineering, Liverpool University.
    Bullough, T.J.
    Department of Materials Science and Engineering, Liverpool University.
    Wagner, J.
    Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastrasse 72, D-79108 Freiburg.
    Jeynes, C.
    Department of Electronic and Electrical Engineering, University of Surrey, Guildford.
    Breuer, S.J.
    Department of Physics, University of Exeter.
    Jones, R.
    Department of Physics, University of Exeter.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    The bonding of CAs acceptors in InxGa1-xAs grown by chemical beam epitaxy using carbon tetrabromide as the source of carbon1996Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 80, nr 12, s. 6754-6760Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    InxGa1-xAs layers (0≤x≤0.37) doped with carbon (>1020 cm-3) were grown on semi-insulating GaAs substrates by chemical beam epitaxy using carbon tetrabromide (CBr4) as the dopant source. Hall measurements imply that all of the carbon was present as CAs for values x up to 0.15. The C acceptors were passivated by exposing samples to a radio frequency hydrogen plasma for periods of up to 6 h. The nearest-neighbor bonding configurations of CAs were investigated by studying the nondegenerate antisymmetric hydrogen stretch mode (A-1 symmetry) and the symmetric XH mode (A+1 symmetry) of the H-CAs pairs using IR absorption and Raman scattering, respectively. Observed modes at 2635 and 450 cm-1 had been assigned to passivated Ga4CAs clusters. New modes at 2550 and 430 cm-1 increased in strength with increasing values of x and are assigned to passivated InGa3CAs clusters. These results were compared with ab initio local density functional theory. Modes due to AlInGaCAs clusters were detected in samples containing grown in Al and In. These results demonstrate that for InGaAs, CBr4 is an efficient C doping source since both In-CAs bonds as well as Ga-CAs bonds are formed, whereas there is no evidence for the formation of In-CAs bonds in samples doped with C derived from trimethylgallium or solid sources

  • 5.
    Bergström, David
    et al.
    Mid Sweden University, Östersund.
    Powell, John
    Laser Expertise Ltd., Acorn Park Industrial Estate, Nottingham.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    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, s. 113504-1Artikel 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.

  • 6.
    Bergström, David
    et al.
    Mid Sweden University, Department of Engineering, Physics and Mathematics.
    Powell, John
    Laser Expertise Ltd., Acorn Park Industrial Estate, Nottingham.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    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 10Artikel 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

  • 7.
    Chernogorova, O.
    et al.
    Baikov Institute of Metallurgy and Materials Science (IMET), Russian Academy of Sciences.
    Drozdova, E.
    Baikov Institute of Metallurgy and Materials Science (IMET), Russian Academy of Sciences.
    Ovchinnikova, I.
    Baikov Institute of Metallurgy and Materials Science (IMET), Russian Academy of Sciences.
    Soldatov, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ekimov, E.
    Vereshchagin Institute for High Pressure Physics RAS, Troitsk.
    Structure and properties of superelastic hard carbon phase created in fullerene-metal composites by high temperature-high pressure treatment2012Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, nr 11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Treatment of a fullerene soot extract and metal (Co) powder mixture under pressure of 5 and 8 GPa at 1000 °C leads to the transformation of fullerites into superelastic hard phase (SHP) and to simultaneous sintering of the powder mixture to nonporous composite material reinforced by the SHP particles. The structure of the SHP particles reveals a topological relation to the initial fullerite crystal morphology. Upon indentation, the SHP particles demonstrate an elastic recovery of up to 96. The universal microhardness of the SHP particles HU=26 GPa, and their microhardness HV = 35 GPa. A high ratio between the microhardness and elastic modulus (HV/E = 0.19-0.21) of the SHP particles makes them perspective candidates for design of materials with superior wear resistance and tribological properties.

  • 8.
    Chijioke, Akobuije D.
    et al.
    Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts.
    Nellis, W. J.
    Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts.
    Soldatov, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Silvera, Isaac F.
    Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts.
    The ruby pressure standard to 150 GPa2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, nr 11, s. 1-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A determination of the ruby high-pressure scale is presented using all available appropriate measurements including our own. Calibration data extend to 150 GPa. A careful consideration of shock-wave-reduced isotherms is given, including corrections for material strength. The data are fitted to the calibration equation P=(A/B)[(/0)B–1] (GPa), with A=1876±6.7, B=10.71±0.14, and is the peak wavelength of the ruby R1 line.

  • 9.
    Grishin, A.
    et al.
    Kungliga tekniska högskolan, KTH.
    Niska, John
    Luleå tekniska universitet.
    Loberg, Bengt
    Weber, Hans
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Straightened voltage effect in high-Tc superconductors1994Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 76, nr 10, s. 6947-6949Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new effect called ``ac-current straightening'' has been observed in ceramic (Bi,Pb)-2223 slabs carrying ac current Idc+Iac cos(ωt). The current-voltage (I-V) characteristics of the ceramic were measured at 77 K at frequencies ranging from 50 to 20 000 Hz. A spectrum analyzer showed a series of high harmonics in the voltage signal as well as a constant voltage drop. The full set of experimental data has been explained theoretically using the Bean-Kim critical state model with a magnetic field dependent critical current jc(H)=jc(0)/(1+H/H0). A low transport ac current gives a voltage linearly proportional to the frequency and quadratically proportional to the ac-current amplitude Iac. It consists of odd harmonics only. If a bias dc current is switched on, then even harmonics and a dc-voltage drop appear. Their amplitudes are proportional to the small parameter Iac/cH0 and depend on the Idc/Iac ratio.

  • 10.
    Gustafsson, Göran
    Luleå tekniska universitet.
    Experiments on shock-wave focusing in an elliptical cavity1987Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 61, nr 11, s. 5193-5195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experimental work on reflection and focusing of weak cylindrical shock waves in a liquid-filled elliptical cavity is presented. The shocks are generated at one focus of the cavity by electrical discharges, and converge at the other focus after reflection in the cavity wall. High-speed photographs of the resulting wave system, which appears to be considerably more complex than the corresponding one in air, are shown and discussed. The results are of interest in the design of a transient water-jet generator, which utilizes the energy in the converging shock wave to produce a fast liquid jet.

  • 11.
    Iwata, H.
    et al.
    Department of Physics and Measurement Technology, Linköping University.
    Lindefelt, U.
    Department of Physics and Measurement Technology, Linköping University.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Cubic polytype inclusions in 4H-SiC2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, nr 3, s. 1577-1585Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multiple stacking faults in 4H-SiC, leading to narrow 3C polytype inclusions along the hexagonal c direction, have been studied using an ab initio supercell approach with 96 atoms per supercell. The number of neighboring stacking faults considered is two, three, and four. The wave functions and the two-dimensional energy bands, located in the band gap and associated with the narrow inclusions, can be reconciled with a planar quantum-well model with quantum-well depth equal to the conduction band offset between 3C- and 4H-SiC. We show that the existence of the electronic dipole moment due to the spontaneous polarization leads to a clear asymmetry of the bound wave functions inside the quantum well, and that the perturbation associated with the change in the dipole moment caused by the 3C-like inclusion accounts for the appearance of very shallow localized states at the valence band edge. We have also calculated the stacking fault energies for successive stacking faults. It is found that the stacking fault energy for two stacking faults in adjacent basal planes is reduced by approximately a factor of 4 relative to that of one isolated stacking fault, indicating that double stacking faults in 4H-SiC could be quite common.

  • 12.
    Iwata, H.P.
    et al.
    Department of Physics and Measurement Technology, Linköping University.
    Lindefelt, U.
    Department of Physics and Measurement Technology, Linköping University.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Ab initio study of 3 C inclusions and stacking fault-stacking fault interactions in 6H-SiC2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 94, nr 8, s. 4972-4979Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ab initio supercell calculations of cubic inclusions in 6H-SiC are performed. The cubic inclusions can be created in perfect 6H-SiC by the propagation of successive partial dislocations having the same Burgers vector in neighboring basal planes, i.e., multiple stacking faults. We have studied the electronic structures and the total energies of 6H-SiC single crystals that contain one, two, three, and four stacking faults, based on density functional theory in local density approximation. Our total energy calculations have revealed that the second stacking fault energy in 6H-SiC is about six to seven times larger than that of an isolated stacking fault, which is actually opposite the trend recently obtained for 4H-SiC [J. Appl. Phys. 93, 1577 (2003)]. The effects of spontaneous polarization on the electronic properties of stacking disorders are examined in detail. The calculated positions of the quantum-well-like localized bands and stacking fault energies of 3C inclusions in 6H-SiC are compared with those previously determined in 4H-SiC, and the possibility of local hexagonal to cubic polytypic transformations is discussed in light of the formation energy and quantum-well action.

  • 13.
    Johansen, T.H.
    et al.
    Olso Universitet.
    Bratsberg, H.
    Oslo universitet.
    Yang, Z.J.
    Oslo universitet.
    Guo, S.J,
    Luleå tekniska universitet.
    Loberg, Bengt
    Transition from elastic to dissipative motion in a magnet--high-T superconductor system1991Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 70, nr 12, s. 7496-7499Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using quasistatic harmonic excitations, we have measured the lateral force between a permanent magnet and a Bi-based ceramic high-Tc superconductor (HTSC) for lateral displacement amplitudes down to 1 µm. We find clear evidence for a transition from elastic (nondissipative) to inelastic interaction, and attribute the effect to flux pinning. The crossover amplitude can easily reach several micrometers, with the consequence that the lateral disturbance of a levitated magnet will decay to this amplitude, whereas further damping will be extremely slow. For applications of HTSCs in magnetic bearing systems this can be a very relevant aspect of the interaction, and it can set the limit for precision positioning of levitated objects

  • 14. Kaplan, Alexander
    An analytical model of metal cutting with a laser beam1996Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 79, nr 5, s. 2198-2208Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The process of cutting metals with a laser beam is described by a mathematical model comprising a set of balance equations for mass, momentum and energy. The molten film at the cutting front is defined as the control volume. The calculation yields average values for the characteristic macroscopic state of the cutting front, such as temperature, melt film velocity and melt film thickness. All relevant parameters of the laser beam and of the process gas flow are considered in the model. Numerical evaluations of the analytical model provide explanations of the process behavior both for inert and for oxygen gas cutting. The narrowing of the kerf width with increasing speed is explained by heat conduction. Furthermore, the model shows that the evaporation temperature is reached at high velocities for thin metal sheets. Using a higher gas pressure increases the diffusion limited oxidation rate and provides higher cutting velocities, while the fraction of oxidized metal decreases substantially with increasing speed.

  • 15.
    Markevich, V.P.
    et al.
    Photon Science Institute, University of Manchester.
    Peaker, A.R.
    Photon Science Institute, University of Manchester.
    Hamilton, B
    Photon Science Institute, University of Manchester.
    Litvinov, V.V.
    Belarusian State University, Minsk.
    Pokotilo, Yu.M.
    Belarusian State University, Minsk.
    Lastovskii, S.B.
    Scientific-Practical Materials Research Center of NAS of Belarus.
    Coutinho, J
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Carvalho, A
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Tin-vacancy complex in germanium2011Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, s. 083705-1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electrically active defects introduced into Ge crystals co-doped with tin and phosphorus atoms by irradiation with 6 MeV electrons have been studied by means of transient capacitance techniques and ab-initio density functional modeling. It is shown that Sn atoms are effective traps for vacancies (V) in the irradiated Ge:Sn+P crystals. The electronic structure of Sn-V is unraveled on the basis of hybrid states from a Sn atom and a divacancy. Unlike the case for Si, Sn-V in Ge is not a donor. A hole trap with 0.19 eV activation energy for hole emission to the valence band is assigned to an acceptor level of the Sn-V complex. The Sn-V complex anneals out upon heat-treatments in the temperature range 50–100 °C. Its disappearance is accompanied by the formation of phosphorus-vacancy centers.

  • 16.
    Matti, Ramiz
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Analysis of laser remote fusion cutting based on a mathematical model2013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, nr 23, artikel-id 233107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser remote fusion cutting is analyzed by the aid of a semi-analytical mathematical model of the processing front. By local calculation of the energy balance between the absorbed laser beam and the heat losses, the three-dimensional vaporization front can be calculated. Based on an empirical model for the melt flow field, from a mass balance, the melt film and the melting front can be derived, however only in a simplified manner and for quasi-steady state conditions. Front waviness and multiple reflections are not modelled. The model enables to compare the similarities, differences, and limits between laser remote fusion cutting, laser remote ablation cutting, and even laser keyhole welding. In contrast to the upper part of the vaporization front, the major part only slightly varies with respect to heat flux, laser power density, absorptivity, and angle of front inclination. Statistical analysis shows that for high cutting speed, the domains of high laser power density contribute much more to the formation of the front than for low speed. The semi-analytical modelling approach offers flexibility to simplify part of the process physics while, for example, sophisticated modelling of the complex focused fibre-guided laser beam is taken into account to enable deeper analysis of the beam interaction. Mechanisms like recast layer generation, absorptivity at a wavy processing front, and melt film formation are studied too.

  • 17.
    Santos, Paolo
    et al.
    Department of Physics and I3N, University of Aveiro, Campus Santiago, 3810-193 Aveiro, Portugal.
    Coutinho, Jose
    Department of Physics and I3N, University of Aveiro, Campus Santiago, 3810-193 Aveiro, Portugal.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    First-principles calculations of iron-hydrogen reactions in silicon2018Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, nr 24, artikel-id 245703Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Controlling the contamination of silicon materials by iron, especially dissolved interstitial iron (Fe-i), is a longstanding problem with recent developments and several open issues. Among these, we have the question whether hydrogen can assist iron diffusion or if significant amounts of substitutional iron (Fe-s) can be created. Using density functional calculations, we explore the structure, formation energies, binding energies, migration, and electronic levels of several FeH complexes in Si. We find that a weakly bound FeiH pair has a migration barrier close to that of isolated Fe-i and a donor level at E-v + 0.5 eV. Conversely, FeiH2 (0/+) is estimated at E-v + 0.33 eV. These findings suggest that the hole trap at E-v + 0.32 eV obtained by capacitance measurements should be assigned to FeiH2 . FesH-related complexes show only deep acceptor activity and are expected to have little effect on minority carrier life-time in p-type Si. The opposite conclusion can be drawn for n-type Si. We find that while in H-free material Fe i defects have lower formation energy than Fe-s , in hydrogenated samples Fe-s -related defects become considerably more stable. This would explain the observation of an electron paramagnetic resonance signal attributed to a FesH-related complex in hydrogenated Si, which was quenched from above 1000 degrees C to iced-water temperature.

  • 18. Söderberg, Hans
    et al.
    Odén, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Molina-Aldareguia, J.M.
    Department of Physics and Measurement Technology, Biology and Chemistry (IFM), Linköping University.
    Hultman, L.
    Thin Film Physics Division, Department of Physics and Measurement Technology, Biology and Chemistry (IFM), Linköping University.
    Nanostructure formation during deposition of TiN/SiNx nanomultilayer films by reactive dual magnetron sputtering2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 97, nr 11, s. 114327-1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multilayer thin films consisting of titanium nitride (TiN) and silicon nitride (SiNx) layers with compositional modulation periodicities between 3.7 and 101.7 nm have been grown on silicon wafers using reactive magnetron sputtering. The TiN and SiNx layer thicknesses were varied between 2-100 nm and 0.1-2.8 nm, respectively. Electron microscopy and x-ray diffraction studies showed that the layering is flat with distinct interfaces. The deposited TiN layers were crystalline and exhibited a preferred 002 orientation for layer thicknesses of 4.5 nm and below. For larger TiN layer thicknesses, a mixed 111/002 preferred orientation was present as the competitive growth favored 111 texture in monolithic TiN films. SiNx layers exhibited an amorphous structure for layer thicknesses ≥0.8 nm; however, cubic crystalline silicon nitride phase was observed for layer thicknesses ≤0.3 nm. The formation of this metastable SiNx phase is explained by epitaxial stabilization to TiN. The microstructure of the multilayers displayed a columnar growth within the TiN layers with intermittent TiN renucleation after each SiNx layer. A nano-brick-wall structure was thus demonstrated over a range of periodicities. As-deposited films exhibited relatively constant residual stress levels of 1.3±0.7 GPa (compressive), independent of the layering. Nanoindentation was used to determine the hardness of the films, and the measurements showed an increase in hardness for the multilayered films compared to those for the monolithic SiNx and TiN films. The hardness results varied between 18 GPa for the monolithic TiN film up to 32 GPa for the hardest multilayer, which corresponds to the presence of cubic SiNx. For larger wavelengths, ≥20 nm, the observed hardness correlated to the layer thickness similar to a Hall-Petch dependence, but with a generalized power of 0.4. Sources of the hardness increase for shorter wavelengths are discussed, e.g., epitaxial stabilization of metastable cubic SiNx, coherency stress, and impeded dislocation activity.

  • 19.
    Thölen, A.R.
    et al.
    Danmarks tekniska universitet.
    Li, Chang-Hai
    Luleå tekniska universitet.
    Easterling, Kenneth
    Luleå tekniska universitet.
    Possible wave formation and martensitic transformation of iron particles in copper single crystals during argon ion bombardment1983Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 54, s. 1067-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin single crystal copper specimens (thickness ~250 nm) containing coherent iron particles (diameter 40-50 nm) have been bombarded with argon ions (5, 80, and 330 keV). During this process some of the iron particles transform to martensite. The transformation was observed near the exposed surface and sometimes also close to the other surface but never in between. This is interpreted in terms of mechanical waves starting from the impact area.

  • 20.
    Tokarev, V.
    et al.
    General Physics Institute of the Russian Academy of Science.
    Kaplan, Alexander
    An analytical modeling of time dependent pulsed laser melting1999Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 86, nr 5, s. 2836-2846Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The one-dimensional time dependent heat conduction equation for surface heating and a phase boundary (the so-called classical Stefan problem) has been solved in the absence of vaporization. For a rectangular laser pulse and constant material parameters, useful solutions have been determined for melt depth as a function of time both during and following the pulse. Based on the model, the intensity dependence of the melt depth is investigated. Two melting regimes-slow and fast-have been identified by comparison with previously reported data for silicon

  • 21.
    Vomiero, Alberto
    et al.
    Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro.
    Marchi, E. Boscolo
    Istituto Nazionale di Fisica Nucleare (INFN).
    Mariotto, G.
    Istituto Nazionale di Fisica della Materia (INFM) and Dipartimento di Fisica, Università di Trento.
    Mea, G. Della
    Istituto Nazionale di Fisica Nucleare (INFN).
    Scandurra, A.
    Laboratorio Superfici e Interfasi, Consorzio Catania Ricerche, Catania.
    Puglisi, O.
    Dipartimento di Scienze Chimiche, Università di Catania.
    The role of N in the resputtering inhibition of Si in W-Si-N reactively sputtered thin layer2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 97, nr 3, artikel-id 34905Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    W-Si-N thin films were synthesized by reactive sputtering of W 5Si 3 target in an Ar/N 2 mixed atmosphere. The nitrogen atomic concentrations within the films ranged between 0 and 60 at. %, as revealed by Rutherford backscattering measurements. At low nitrogen atom fluxes an intense Si resputtering was observed, leading to the formation of a W-rich layer with respect to target composition. The characterization of plasma parameters during the deposition, carried out with the help of a Langmuir probe, suggests that the Ar neutral atoms reflected by W atoms of the target are the main responsibilities of Si resputtering with respect to charged species, whose resputtering effect is less important. The inhibition of this phenomenon takes place with growing nitrogen concentration. The preferential formation of Si-N bonds with respect to W-N bonds was unveiled by both x-ray photoelectron spectroscopy and Fourier transform infrared absorption spectroscopy. This also justifies the inhibition of Si resputtering. A comparison with literature data concerning W-Si-N systems sputtered at different plasma conditions was performed in order to highlight the influence of plasma parameters on the composition of the layers. © 2005 American Institute of Physics.

  • 22.
    Vomiero, Alberto
    et al.
    INFN Laboratori Nazionali di Legnaro.
    Marchi, E. Boscolo
    INFN Laboratori Nazionali di Legnaro.
    Quaranta, A.
    Mea, G. Della
    Brusa, R. S.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Mariotto, G.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Felisari, L.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Frabboni, S.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Tonini, R.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Ottaviani, G.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Mattei, G.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Scandurra, A.
    Superlab-Consorzio Catania Ricerche.
    Puglisi, O.
    Dipartimento di Scienze Chimiche, Università di Catania.
    Structural properties of reactively sputtered W-Si-N thin films2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, nr 3, artikel-id 33505Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tungsten-silicon-nitrogen, W-Si-N, ternary thin films have been reactively sputter deposited from W5 Si3 and W Si2 targets using several nitrogen partial pressures. The films have been thermal annealed in the 600-1000 °C temperature range and a wide region of the W-Si-N ternary phase diagram has been explored by changing the N2 Ar ratio during the deposition. Multitechnique approach was adopted for the analysis of the samples. Composition has been determined via ion beam analysis; chemical states were investigated using x-ray photoelectron spectroscopy (XPS); crystalline structure was studied using transmission electron microscopy (TEM) and x-ray diffraction (XRD) and surface morphology by scanning electron microscope. The films deposited in pure argon atmosphere are tungsten rich and approach the target contents as N2 Ar ratio is varied during deposition. Tungsten enrichment in the films is caused by resputtering of silicon which can be inhibited by the formation of silicon nitride, allowing films with SiW ratio closer to the target compositions. The higher capability to form nitrides with silicon than with tungsten favors enhancement of nitrogen content in samples deposited from the silicon rich target (W Si2). The samples with excess nitrogen content have shown losses of this element after thermal treatment. XPS measurements show a break of W-N bonds caused by thermal instability of tungsten nitrides. TEM and XRD revealed the segregation of tungsten in form of metallic or silicide nanoclusters in samples with low nitrogen content (W58 Si21 N21 and W24 Si42 N34). High amounts of nitrogen were revealed to be highly effective in inhibiting metallic cluster coalescence. Measurements of electrical resistivity of as deposited films were performed using four point probe technique. They were found to lie in the range between 0.4 and 79 m cm depending on sample composition. © 2007 American Institute of Physics.

  • 23.
    Wright, E.
    et al.
    Department of Physics and I3N, University of Aveiro, Campus Santiago.
    Coutinho, José A.
    Department of Physics, I3N, University of Aveiro, Campus Santiago, Department of Physics.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Torres, Vitor J. B.
    Department of Physics, University of Aveiro, Department of Physics and I3N, University of Aveiro, Campus Santiago.
    Mössbauer parameters of Fe-related defects in group-IV semiconductors: First principles calculations2016Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, nr 18, artikel-id 181509Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We employ a combination of pseudopotential and all-electron density functional calculations, to relate the structure of defects in supercells to the isomer shifts and quadrupole splittings observed in Mossbauer spectroscopy experiments. The methodology is comprehensively reviewed and applied to the technologically relevant case of iron-related defects in silicon, and to other group-IV hosts to a lesser degree. Investigated defects include interstitial and substitutional iron, iron-boron pairs, iron-vacancy, and iron-divacancy. We find that, in general, agreement between the calculations and Mossbauer data is within a 10% error bar. Nonetheless, we show that the methodology can be used to make accurate assignments, including to separate peaks of similar defects in slightly different environments.

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