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  • 1.
    Adamovic, Dragan
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Chirita, Valeriu
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Münger, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Hultman, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Greene, J.E.
    Materials Science Department and the Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Kinetic pathways leading to layer-by-layer growth from hyperthermal atoms: A Multibillion time step molecular dynamics study2007Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 76, s. 115418-115425Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We employ multibillion time step embedded-atom molecular dynamics simulations to investigate the homoepitaxial growth of Pt(111) from hyperthermal Pt atoms (EPt=0.2–50eV) using deposition fluxes approaching experimental conditions. Calculated antiphase diffraction intensity oscillations, based on adatom coverages as a function of time, reveal a transition from a three-dimensional multilayer growth mode with EPt<20eV to a layer-by-layer growth with EPt≥20eV. We isolate the effects of irradiation-induced processes and thermally activated mass transport during deposition in order to identify the mechanisms responsible for promoting layer-by-layer growth. Direct evidence is provided to show that the observed transition in growth modes is primarily due to irradiation-induced processes which occur during the 10ps following the arrival of each hyperthermal atom. The kinetic pathways leading to the transition involve both enhanced intralayer and interlayer adatom transport, direct incorporation of energetic atoms into clusters, and cluster disruption leading to increased terrace supersaturation.

  • 2.
    Adamovic, Dragan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Chirita, Valeriu
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Greene, Joe
    Controlled intra- and interlayer mass transport during low-energy Pt(111) homoepitaxyManuskript (Annet vitenskapelig)
  • 3.
    Adamovic, Dragan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Greene, Joe
    University of Illinois.
    Enhanced intra- and interlayer mass transport on Pt(111) via 5 - 50 eV Pt atom impacts on two-dimensional Pt clusters2006Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, nr 4, s. 2235-2243Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Embedded-atom molecular dynamics simulations were used to investigate the effects of low-energy (5–50 eV) normally-incident self-ion irradiation of two-dimensional compact Pt3, Pt7, Pt19, and Pt37 clusters on Pt(111). We follow atomistic pathways leading to bombardment-induced intra- and interlayer mass transport. The results can be described in terms of three impact energy regimes. With E ≤ 20 eV, we observe an increase in 2D island dimensions and negligible residual point defect formation. As the impact energy is raised above 20 eV, we observe an increase in irradiation-induced lateral mass transport, a decrease in island size, and the activation of interlayer processes. For E ≥ 35 eV, this trend continues, but point defects, in the form of surface vacancies, are also formed. The results illustrate the richness of the dynamical interaction mechanisms occurring among incident energetic species, target clusters, and substrate atoms, leading to island preservation, reconfiguration, disruption and/or residual point defects formation. We discuss the significance of these results in terms of thin film growth.

  • 4.
    Adamovic, Dragan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Greene, Joe
    University of Illinois.
    Low-energy ion irradiation during film growth: Kinetic pathways leading to enhanced adatom migration rates2005Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, s. 211915-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Embedded-atom molecular dynamics simulations are used to investigate the effects of low-energy self-ion irradiation of Pt adatoms on Pt(111). Here, we concentrate on self-bombardment dynamics, i.e., isolating and monitoring the atomic processes, induced by normally incident Pt atoms with energies E ranging from 5 to 50 eV, that can affect intra- and interlayer mass transport.. We find that adatom scattering, surface channeling, and dimer formation occur at all energies. Atomic intermixing events involving incident and terrace atoms are observed at energies 15  eV, while the collateral formation of residual surface vacancies is observed only with E>40  eV. The overall effect of low-energy self-ion irradiation is to enhance lateral adatom and terrace atom migration. ©2005 American Institute of Physics

  • 5.
    Andersson, Jon M.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Wallin, Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, E. Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Ab initio calculations on the effects of additives on alumina phase stability2005Inngår i: Physical review. B, Condensed matter and materials physics, ISSN 1098-0121, Vol. 71, nr 014101, s. 014101-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of substitutional additives on the properties and phase stability of - and -alumina (Al2O3), are investigated by density functional theory total energy calculations. The dopants explored are 5 at. % of Cr, Mo, Co, and As substituting for Al, respectively, N and S substituting for O, in the and lattices. Overall, the results show that it is possible to shift, and even reverse, the relative stability between - and -alumina by substitutional additives. The alumina bulk moduli are, in general, only slightly affected by the dopants but density of states profiles reveal additional peaks in the alumina band gaps. We also show that phase separations into pure oxides are energetically favored over doped alumina formation, and we present results on a number of previously unstudied binary oxides.

  • 6.
    Andersson, Jon M.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Wallin, Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, E. Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Molecular content of the deposition flux during reactive Ar/O2 magnetron sputtering of Al2006Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, nr 05, s. Art. No. 054101 JAN 30 2006-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The deposition flux obtained during reactive radio frequency magnetron sputtering of an Al target in Ar/O2 gas mixtures was studied by mass spectrometry. The results show significant amounts of molecular AlO+ (up to 10% of the Al+ flux) in the ionic flux incident onto the substrate. In the presence of ~10–4 Pa H2O additional OH+ and AlOH+ were detected, amounting to up to about 100% and 30% of the Al+ flux, respectively. Since the ions represent a small fraction of the total deposition flux, an estimation of the neutral content was also made. These calculations show that, due to the higher ionization probability of Al, the amount of neutral AlO in the deposition flux is of the order of, or even higher than, the amount of Al. These findings might be of great aid when explaining the alumina thin film growth process.

  • 7.
    Andersson, Jon M.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Wallin, Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Energy distributions of positive and negative ions during magnetron sputtering of an Al target in Ar/O2 mixtures2006Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 100, nr 3, s. Art. No. 033305 AUG 1 2006-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ion flux obtained during reactive magnetron sputtering of an Al target in Ar/O2 gas mixtures was studied by energy-resolved mass spectrometry, as a function of the total and O2 partial pressures. The positive ions of film-forming species exhibited bimodal energy distributions, both for direct current and radio frequency discharges, with the higher energy ions most likely originating from sputtered neutrals. For the negative oxygen ions a high-energy peak was observed, corresponding to ions formed at the target surface and accelerated towards the substrate over the sheath potential. As the total pressure was increased the high-energy peaks diminished due to gas-phase scattering. Based on these results, the role of energetic bombardment for the phase constituent of alumina thin films are discussed.

  • 8.
    Andersson, Jon Martin
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Wallin, Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Kreissig, U.
    Institute for Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf, PF 510119, D-01314 Dresden, Germany.
    Münger, E. Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Phase control of Al2O3 thin films grown at low temperatures2006Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 513, nr 1-2, s. 57-59Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Low-temperature growth (500 °C) of α-Al2O3 thin films by reactive magnetron sputtering was achieved for the first time. The films were grown onto Cr2O3 nucleation layers and the effects of the total and O2 partial pressures were investigated. At 0.33 Pa total pressure and ≥ 16 mPa O2 partial pressure α-Al2O3 films formed, while at lower O2 pressure or higher total pressure (0.67 Pa), only γ phase was detected in the films (which were all stoichiometric). Based on these results we suggest that α phase formation was promoted by a high energetic bombardment of the growth surface. This implies that the phase content of Al2O3 films can be controlled by controlling the energy of the depositing species. The effect of residual H2O (10− 4 Pa) on the films was also studied, showing no change in phase content and no incorporated H (< 0.1%). Overall, these results are of fundamental importance in the further development of low-temperature Al2O3 growth processes.

  • 9.
    Bartkowiak, M.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan. A. Mickiewicz University, Poznań, Poland.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Chao, K. A
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    High-Density Expansion for the Spinless Fermion Model II: Second and Third Order in 1/z1988Inngår i: International Journal of Modern Physics B, ISSN 0217-9792, Vol. 2, nr 03-04, s. 521-536Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The selfconsistent high-density expansion for thermodynamic quantities of the quantum spin-polarized fermion lattice gas, derived in the preceding paper, is extended to higher orders. The (1/z)2terms in the free energy are evaluated by summing two-loop diagrams and the corresponding equation for critical temperature in the classical limit is discussed. Ground state phase diagram of the system for arbitrary electron density is derived in the first and second order of the expansion. Properties of the half-filled, one-dimensional spinless fermion model at T = 0, obtained here in the first three orders in 1/z, are compared with the results of exact calculations and of other approximate methods. This provides a test for the unrenormalized high-density expansion method.

  • 10.
    BARTKOWIAK, M
    et al.
    University of Trondheim, Norway.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    CHAO, KA
    University of Trondheim, Norway.
    MICNAS, R
    A. Mickiewicz University, Institute of Physics, Poland.
    HIGH - DENSITY EXPANSION FOR ELECTRON-SYSTEMS1990Inngår i: APPLICATIONS OF STATISTICAL AND FIELD THEORY METHODS TO CONDENSED MATTER, 1990, Vol. 218Konferansepaper (Fagfellevurdert)
  • 11.
    Bartkowiak, M
    et al.
    University of Trondheim, Norway.
    Münger, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Chao, Kuong-An
    University of Trondheim, Norway.
    High-Density Expansion for the Spinless Fermion Model III: Green-Functions1990Inngår i: International Journal of Modern Physics B, ISSN 0217-9792, Vol. 4, nr 13, s. 2025-2040Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The single-particle electron Green's function and the charge-fluctuation Green's function for the spin-polarized fermion lattice gas are calculated within the framework of the high-density expansion up to the first order in 1/z. Violation of some conditions of consistency of diagrammatic perturbation expansion approximation schemes are discussed. Relations between the Green's functions and corresponding approximate free energy are established. Two kinds of approximations for Green's functions for the charge ordered phase are constructed and applied to determine the band structure of the spinless fermion model. The Green's functions for the nonordered phase are used to study the phase diagram of the model for finite temperatures and arbitrary band filling.

     

  • 12.
    Bartkowiak, M.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan. Adam Mickiewicz University, Poznań, Poland .
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Micnas, R.
    Adam Mickiewicz University, Poznań, Poland .
    High-Density Expansion for the Spinless Fermion Model I: First Order in 1/z and Horwitz-Callen Renormalization1988Inngår i: International Journal of Modern Physics B, ISSN 0217-9792, Vol. 2, nr 03-04, s. 483-520Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A diagrammatic technique for Hubbard's operators is employed to perform systematically the high-density expansion for the three-dimensional spinless fermion model. The molecular field theory is obtained by the zero-order renormalization of blocks. Summation of the first order diagrams is carried out in both selfconsistent and correctional way. It turns out that the charge ordering parameter, calculated self-consistently, has a jump for a certain medial temperature. We have also shown, that the Horwitz-Callen renormalization leads to the first or second order phase transition, depending on t/W and fails when this ratio is large enough. The phase diagrams of the system for the half-filled band case, derived in both unrenormalized and renormalized first order of high-density expansion are presented.

  • 13.
    Carlberg, M H
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Atomistic study of defect generation mechanisms in Mo/W superlattices1996Inngår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 112, nr 1-4, s. 109-111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work we report the investigation of defect generation in Mo/W superlattices (SL). The study has been carried out using molecular dynamics (MD) and the embedded atom (EAM) potential. Mechanisms for the generation of observed defect patterns are proposed.

  • 14.
    Carlberg, M H
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Defects and energy accommodation in epitaxial sputter deposited Mo/W superlattices studied by molecular dynamics1998Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 317, nr 1-2, s. 10-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report here the results of a Molecular Dynamics-Embedded Atom Method-investigation of the pathways generating point defects in Mo/W superlattices during bombardment with energetic (50 to 200 eV) Ar and Kr neutrals. Energy accommodation coefficients are computed for the different structures and are found to be roughly independent of the incident energy, and substantially higher for structures with Mo on top. Several different types of defects are shown, and two general processes generating those are discussed. Trapping of the incoming noble gas was observed for the case of Kr impinging on structures with Mo as the top monolayer; this is interpreted as an effect of the small mass difference between the Mo and the Kr atoms. An increase in atomic mass of the gas translates into a more disparate behaviour of the studied structures. The energy exchange with the surface layer dictates the behaviour of the superlattice; this is accentuated when bombarding with the heavier gas, Kr. (C) 1998 Elsevier Science S.A.

  • 15.
    Carlberg, M H
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Molecular-dynamics studies of defect generation in epitaxial Mo/W superlattices1996Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 54, nr 3, s. 2217-2224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An investigation of defect generation at the interface during growth of epitaxial (100) oriented Mo/W superlattices by ion-assisted deposition has been carried out using molecular-dynamics simulations. The influence of the impact parameter within the irreducible bcc unit cell [001] surface and the incident ion energy on the energy accommodation, the dynamics of energy transfer, and energy dissipation are discussed. A detailed model of the generation of point defects is presented and the influence of materials upon the type and the number of defects as well as the energy accommodation of the superlattice is revealed. It is shown that the behavior of the superlattice as a whole is largely dominated by the material in the surface monolayer.

  • 16.
    Carlberg, M H
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Dynamics of self-interstitial structures in body-centred-cubic W studied by molecular dynamics simulation2000Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 12, nr 1, s. 79-86Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study concerns a molecular dynamics (MD) simulation, using the embedded-atom method (EAM), of the self-diffusion of an interstitial in the bcc metal tungsten (W) at 2000 K. It is found that the interstitial moves only along (111) diagonals and that the switches to other nonparallel directions take place through a two-dimensional process. The (011) dumb-bell is central to this process. Movement along the (111) diagonals takes place through (111) crowdions occupying 2-6 lattice sites. The probabilities of a direction switch and a move are 0.249 and 0.751, respectively. Translating the complicated movement mechanism into the simple picture of interstitial hopping between lattice points, the diffusion velocity is calculated to be 520 m s(-1), and the activation energy for the interstitial self-diffusion is calculated to be 0.54 eV/interstitial.

  • 17.
    Carlberg, M H
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Self-interstitial structures in body-centred-cubic W studied by molecular dynamics simulation1999Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 11, nr 34, s. 6509-6514Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper reports a simulation study of the detailed structure of an interstitial in a body-centred-cubic (bcc) metal, tungsten (W), using molecular dynamics and the embedded-atom method. Several distinct configurations can be discerned, including the well-known split-interstitial [011] dumb-bell. The [111] crowdion is also observed, as is a set of similar, one-dimensional, defect configurations. These are grouped into a proposed classification scheme, in which the traditional crowdion is revealed as part of a whole family. The defect energies of the various configurations are computed, and comparisons are made with bce iron (Fe) results. The [011] dumb-bell is the energetically most favourable configuration in W. It is found to have a radius of approximately one W lattice constant, 3.16 Angstrom.

  • 18.
    Chirita, Valeriu
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Greene, J.E.
    Materials Science Department, Materials Research Laboratory, University of Illinois, 104 South Goodwin Avenue, Urbana, IL 61801, United States.
    Sundgren, J.-E.
    Cluster diffusion and surface morphological transitions on Pt (111) via reptation and concerted motion2000Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 370, nr 1, s. 179-185Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Embedded-atom molecular dynamics simulations were used to follow the diffusion dynamics of compact Pt clusters with up to 19 atoms on Pt (111) surfaces. The results reveal a novel cluster diffusion mechanism, involving successive shear translations of adjacent subcluster regions, which give rise to reptation, a snake-like gliding motion. We show that for compact clusters with 4 to 6 atoms, this mechanism competes energetically with that of island diffusion through concerted motion. However, as the cluster size increases from > 7 to ? 20 atoms, reptation becomes the energetically favored diffusion mechanism. The concerted shear motion of subcluster regions, leading to reptation, is also shown to play a significant role in dendritic-to-compact morphological transitions of Pt island.

  • 19.
    Chirita, Valeriu
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Greene, Joseph E
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Sundgren, J E
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Reptation: a mechanism for cluster migration on (111) face-centered-cubic metal surfaces1999Inngår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 436, nr 1-3, s. L641-L647Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Embedded-atom molecular-dynamics simulations were used to follow the diffusion dynamics of compact platinum clusters with up to 19 atoms on Pt(lll). The results reveal a cluster diffusion mechanism on (111) face-centered-cubic (fcc) surfaces involving successive shear translations of adjacent subcluster regions giving rise to reptation, a snake-like gliding motion. We show that for compact clusters with <7 atoms, this mechanism competes energetically with that of island diffusion through concerted motion. However, for cluster sizes of between 8 and similar or equal to 20 atoms, reptation becomes energetically favorable, especially for elongated clusters. Reptation is also shown to be an important migration mechanism for fractal (randomly ramified) and dendritic (symmetrically branched) islands. (C) 1999 Elsevier Science B.V. All rights reserved.

  • 20.
    Chirita, Valeriu
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Sundgren, Jan-Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Greene, Joseph E
    University of Illinois, Urbana, USA.
    Enhanced cluster mobilities on Pt(111) during film growth from the vapor phase1998Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 72, nr 1, s. 127-129Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use molecular dynamics simulations to follow the dynamics of small two-dimensional Pt clusters on Pt(111) at 1000 K. While close-packed Pt-7 heptamers are extremely stable structures, the addition of a single cluster vacancy or an on-top adatom immediately results in intracluster bond breaking, reconfigurations, rotations, the introduction of stacking faults, and greatly enhanced cluster diffusion rates. Mapping center-of-mass motion for total simulation times >145 ns revealed increases in cluster velocities by more than an order of magnitude with cluster migration occurring primarily by concerted motion and a novel diffusion mechanism involving double shearing of dimers/trimers. Contrary to some previous reports, edge-atom diffusion plays only a minor role. (C) 1998 American Institute of Physics.

  • 21.
    Curtsdotter, Alva
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Norberg, Jon
    Department of Systems Ecology, Stockholm University/Stockholm Resilience Centre, Stockholm University, Sweden.
    Åkesson, Anna
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Ebenman, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    The strength of interspecific competition modulates the eco-evolutionary response to climate change2014Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Climate change is predicted to have major implications for global biodiversity. Dispersal and evolution may become crucial for species survival, as species must either adapt or migrate to track the changing climate. However, migration and evolution do not occur in vacuum – the biotic community in which these processes play out may modulate their effect on biodiversity. Here, we use an eco-evolutionary, spatially explicit, multi-species model that allows us to examine the interactive effects of competition, adaptation and dispersal on species richness in plant communities under global warming. We find that there is a larger decline in global species richness when interspecific competition is strong. Furthermore, there is a three-way interaction between interspecific competition, evolution and dispersal that creates a complex pattern of biodiversity responses, in which both evolution and dispersal can either increase or decrease the magnitude of species loss. This interaction arises for at least two reasons: 1) different levels of dispersal, evolution and competition creates differences in local and global community structure before climate change, and 2) competitive interactions determine whether the benefits of dispersal and/or evolution (climate tracking and adaptation) outweighs the risks (competitive exclusion).

  • 22.
    Ekeroth, Sebastian
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Ikeda, Shuga
    Department of Intelligent Mechanical Systems, Tokyo Metropolitan University, Tokyo, Japan.
    Boyd, Robert
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Shimizu, Tetsuhide
    Department of Intelligent Mechanical Systems, Tokyo Metropolitan University, Tokyo, Japan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Impact of nanoparticle magnetization on the 3D formation of dual-phase Ni/NiO nanoparticle-based nanotrusses2019Inngår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 21, nr 11, artikkel-id 21:228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Magnetic nanoparticles with average size 30 nm were utilized to build three-dimensional framework structures—nanotrusses. In dual-phase Ni/NiO nanoparticles, there is a strong correlation between the amount of magnetic Ni and the final size and shape of the nanotruss. As it decreases, the length of the individual nanowires within the trusses also decreases, caused by a higher degree of branching of the wires. The position and orientation of the non-magnetic material within the truss structure was also investigated for the different phase compositions. For lower concentrations of NiO phase, the electrically conducting Ni-wire framework is maintained through the preferential bonding between the Ni crystals. For larger concentrations of NiO phase, the Ni-wire framework is interrupted by the NiO. The ability to use nanoparticles that are only partly oxidized in the growth of nanotruss structures is of great importance. It opens the possibility for using not only magnetic metals such as pure Ni, Fe, and Co, but also to use dual-phase nanoparticles that can strongly increase the efficiency of e.g. catalytic electrodes and fuel cells.

  • 23.
    Ekeroth, Sebastian
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Boyd, Robert
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Ekspong, Joakim
    Umeå Univ, Sweden.
    Wågberg, Thomas
    Umeå Univ, Sweden.
    Edman, Ludvig
    Umeå Univ, Sweden.
    Brenning, Nils
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. KTH Royal Inst Technol, Sweden.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Catalytic Nanotruss Structures Realized by Magnetic Self-Assembly in Pulsed Plasma2018Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, nr 5, s. 3132-3137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tunable nanostructures that feature a high surface area are firmly attached to a conducting substrate and can be fabricated efficiently over significant areas, which are of interest for a wide variety of applications in, for instance, energy storage and catalysis. We present a novel approach to fabricate Fe nanoparticles using a pulsed-plasma process and their subsequent guidance and self-organization into well-defined nanostructures on a substrate of choice by the use of an external magnetic field. A systematic analysis and study of the growth procedure demonstrate that nondesired nanoparticle agglomeration in the plasma phase is hindered by electrostatic repulsion, that a polydisperse nanoparticle distribution is a consequence of the magnetic collection, and that the formation of highly networked nanotruss structures is a direct result of the polydisperse nanoparticle distribution. The nanoparticles in the nanotruss are strongly connected, and their outer surfaces are covered with a 2 nm layer of iron oxide. A 10 mu m thick nanotruss structure was grown on a lightweight, flexible and conducting carbon-paper substrate, which enabled the efficient production of H-2 gas from water splitting at a low overpotential of 210 mV and at a current density of 10 mA/cm(2).

  • 24.
    Eklöf, Anna
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Kaneryd, Linda
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Climate change in metacommunities: dispersal gives double-sided effects on persistence2012Inngår i: Philosphical Transactions of the Royal Society B, ISSN 1471-2970, Vol. 367, nr 1605, s. 2945-2954Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Climate change is increasingly affecting the structure and dynamics of ecological communities bothat local and at regional scales, and this can be expected to have important consequences for theirrobustness and long-term persistence. The aim of the present work is to analyse how the spatialstructure of the landscape and dispersal patterns of species (dispersal rate and average dispersal distance)affects metacommunity response to two disturbances: (i) increased mortality during dispersaland (ii) local species extinction. We analyse the disturbances both in isolation and in combination.Using a spatially and dynamically explicit metacommunity model, we find that the effect of dispersalon metacommunity persistence is two-sided: on the one hand, high dispersal significantly reducesthe risk of bottom-up extinction cascades following the local removal of a species; on the otherhand, when dispersal imposes a risk to the dispersing individuals, high dispersal increases extinctionrisks, especially when dispersal is global. Large-bodied species with long generation times at thehighest trophic level are particularly vulnerable to extinction when dispersal involves a risk. Thissuggests that decreasing the mortality risk of dispersing individuals by improving the quality ofthe habitat matrix may greatly increase the robustness of metacommunities.

  • 25.
    Eklöf, Anna
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Ebenman, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Effects of dispersal on local extinctions in multi-trophic metacommunitiesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    As a result of habitat destruction many ecological communities have a fragmented distribution and are built up of partially isolated local communities connected through dispersal of interacting species. The dynamics of such metacommunities is governed both by local processes (interactions among species coexisting within habitat patches) and regional processes (movement of species among habitat patches). Earlier theoretical work on simple metacommunities have mainly focused on the positive effects of space and dispersal for the coexistence of interacting species and hence for local and regional species diversity. However, it is plausible that dispersal might also pose some kind of risk to the dispersing individuals. Here we explore how such risks might affect the dynamics of metacommunities. We develop spatially and dynamically explicit models to investigate how the trophic structure (connectance) of local communities, the spatial structure of the metacommunity and the dispersal characteristics of species affect species extinction risks. Species extinction risks in these open communities are measured relative to the extinction risks in closed communities (i.e. no dispersal). We show that the introduction of dispersal among initially closed local communities might lead to increased probability of local species extinction. The effects of dispersal depend on migration rate, movement pattern of individuals and the density of patches in the landscape. Specifically, when dispersal involves a risk, high migration rates, global dispersal and low patch density will all lead to increased probability of local species extinctions. Furthermore, the trophic structure of local communities plays a significant role in the response of metacommunities to changes in the regional processes.

  • 26.
    Eklöf, Anna
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Kaneryd, Linda
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Ebenman, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Can dispersal rescue metacommunities from extinction cascades?Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Climate change and habitat loss are increasingly affecting the structure and dynamics of ecological communities both at the local and regional scale. Changes in the spatial structure of landscapes as well as in the trophic structure of local communities can be expected to have important consequences for the long-term persistence of species in metacommunities. The aim of the present work is to investigate how the spatial structure of the landscape (patch density) and dispersal patterns of species (migration rate and dispersal distance) affect a metacommunities response to local loss of species and to increased mortality of individuals during dispersal. Using a spatially and dynamically explicit metacommunity model we find that the effect of dispersal on metacommunity persistence is two-sided: on the one hand, when dispersal involves no risk, high migration rate significantly reduces the risk of bottom-up extinction cascades following the local removal of a species. The explanation for this is that recolonization rates of the locally removed species increases with increasing migration rate. On the other hand, when dispersal imposes a risk to the dispersing individuals, high migration rate increases extinction risks, especially when dispersal is global (long dispersal distances). Largebodied species with long generation times at the highest trophic level are particularly vulnerable to extinction when dispersal involves a risk. These results suggest that decreasing the mortality risk of dispersing individuals by improving the quality of the habitat matrix might greatly increase the robustness of metacommunities to local loss of species by enhancing recolonizations and rescue effects.

  • 27.
    Elofsson, Viktor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Magnfält, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Sarakinos, Kostas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Unravelling the Physical Mechanisms that Determine Microstructural Evolution of Ultrathin Volmer-Weber Films2014Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, nr 4, s. 044302-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 28.
    Johansson, M P
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ivanov, Ivan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Schutze, A
    Fraunhofer‐Institute for Surface Engineering and Thin Films, Braunschweig, Germany.
    Low-temperature deposition of cubic BN: C films by unbalanced direct current magnetron sputtering of a B4C target1996Inngår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 14, nr 6, s. 3100-3107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Controllable-unbalanced de magnetron sputtering of a B4C target in mixed Ar-N-2 discharges has been used to deposit BN:C thin films with carbon concentrations in the range of 5-21 at, % on Si(001) substrates. The variation of the nitrogen gas consumption with nitrogen partial pressure was used to determine the sorption capacity of the sputtering source and was then correlated to the film discharge plasma density near the substrate in a wide range. Hence, the ion flux J(i) of primary Ar+ and N-2(+) ions accelerated to the substrate by an applied negative substrate bias could be varied while keeping the deposition flux J(n) (the sum of film building species, B, C, and N atoms) near constant. BN:C films were grown at large ion-to-neutral flux ratios 3 less than or equal to J(i)/J(n) less than or equal to 24, ion energies E(i) less than or equal to 500 eV, and substrate temperatures 150 less than or equal to T-s less than or equal to 350 degrees C. The phase and elemental composition of as-deposited BN:C films were characterized by Fourier transform infrared spectroscopy and wavelength dispersive x-ray spectroscopy, respectively. Deposition of cubic phase c-BN:C containing 5-7 at. % of C is demonstrated under conditions of low energy (110 eV) ion bombardment, a high ion-to-atom arrival rate ration (J(i)/J(n) similar to 24), and low growth temperatures (similar to 150 degrees C). (C) 1996 American Vacuum Society.

  • 29.
    Kaneryd, Linda
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Borrvall, Charlotte
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Berg, Sofia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Curtsdotter, Alva
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Eklöf, Anna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Hauzy, Céline
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Jonsson, Tomas
    Skövde University, Sweden.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Setzer, Malin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Säterberg, Torbjörn
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Ebenman, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Species-rich ecosystems are vulnerable to cascading extinctions in an indreasingly variable world2012Inngår i: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 2, nr 4, s. 858-874Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Global warming leads to increased intensity and frequency of weather extremes. Such increased environmental variability might in turn result in increased variation in the demographic rates of interacting species with potentially important consequences for the dynamics of food-webs. Using a theoretical approach we here explore the response of food-webs to a highly variable environment. We investigate how species richness and correlation in the responses of species to environmental fluctuations affect the risk of extinction cascades. We find that the risk of extinction cascades increases with increasing species richness, especially when correlation among species is low. Initial extinctions of primary producer species unleash bottom-up extinction cascades, especially in webs with specialist consumers. In this sense, species-rich ecosystems are less robust to increasing levels of environmental variability than species-poor ones. Our study thus suggests that highly species-rich ecosystems like coral reefs and tropical rainforests might be particularly vulnerable to increased climate variability.

  • 30.
    Kaneryd, Linda
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Ebenman, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Robustness of food webs whose structures have been shaped by extinctions in the past2011Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Extinctions of species might lead to changes in the trophic structure of food webs with consequences for the robustness of the webs. Using a theoretical approach we here investigate 1) how ‘natural’ extinctions of species in a variable environment affect the trophic structure of food webs and 2) which consequences these structural changes will have for the topological and dynamical robustness of the webs to further, future disturbances. We show that food webs whose structure have been shaped by extinctions in the past (disassembled webs) are structurally different and more robust to disturbances (species deletion and exposure to high levels of environmental variability) than food webs of equal size (number of species) that have not gone through a phase of disassembly. The increased robustness of the disassembled webs is due to the preservation of certain link structures, structures that have been found to promote topological and dynamical stability. Thus, our results suggest that ‘natural’ extinctions lead to changes in the trophic structure of food webs which make them more resistant to future perturbations.

  • 31.
    Kaneryd, Linda
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Eklöf, Anna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Ebenman, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Risk of global extinctions in metacommunities exposed to a highly variable environment: local and spatial processesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Here we analyze how metacommunities (a set of local communities coupled by species dispersal) in spatially explicit landscapes respond to environmental variation. We examine how this response is affected by 1) species richness in the local communities, 2) the degree of correlation in species response to the environmental variation both between species within patches (species correlation) and among patches (spatial correlation) and 3) dispersal pattern of species. We find that the risk of global extinction increases with increasing species richness in the local communities and with decreasing correlation among species in their response to environmental fluctuations. We also show that the pattern of spatial correlation is of great importance; the risk of global extinctions increases with increasing spatial correlation. Moreover, we find that the pattern and rate of dispersal are important; a high migration rate in combination with localized dispersal decrease the risk of global extinctions whereas a global dispersal pattern increases the risk of global extinctions. When dispersal is global the subpopulations of a species become more synchronized which reduces the potential for a patch to become recolonized following extinctions. We also demonstrate the importance of both local and spatial processes when examining the temporal stability of primary production at the scale of metapopulations, local communities and metacommunities.

  • 32.
    Lü, Bo
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Elofsson, Viktor
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Sarakinos, Kostas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Dynamic competition between island growth and coalescence in metal-on-insulator deposition2014Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, nr 16, s. 163107-1-163107-5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 33.
    Lü, Bo
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, E. Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Sarakinos, Kostas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Growth regimes during metal-on-insulator deposition using pulsed vapor fluxes2014Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

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

  • 34.
    Lü, Bo
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanodesign. Linköpings universitet, Tekniska fakulteten.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Sarakinos, Kostas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanodesign. Linköpings universitet, Tekniska fakulteten.
    Coalescence-controlled and coalescence-free growth regimes during deposition of pulsed metal vapor fluxes on insulating surfaces2015Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, nr 13, artikkel-id 134304Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The morphology and physical properties of thin films deposited by vapor condensation on solid surfaces are predominantly set by the processes of island nucleation, growth, and coalescence. When deposition is performed using pulsed vapor fluxes, three distinct nucleation regimes are known to exist depending on the temporal profile of the flux. These regimes can be accessed by tuning deposition conditions; however, their effect on film microstructure becomes marginal when coalescence sets in and erases morphological features obtained during nucleation. By preventing coalescence from being completed, these nucleation regimes can be used to control microstructure evolution and thus access a larger palette of film morphological features. Recently, we derived the quantitative criterion to stop coalescence during continuous metal vapor flux deposition on insulating surfaceswhich typically yields 3-dimensional growthby describing analytically the competition between island growth by atomic incorporation and the coalescence rate of islands [Lu et al., Appl. Phys. Lett. 105, 163107 (2014)]. Here, we develop the analytical framework for entering a coalescence-free growth regime for metal vapor deposition on insulating substrates using pulsed vapor fluxes, showing that there exist three distinct criteria for suppressing coalescence that correspond to the three nucleation regimes of pulsed vapor flux deposition. The theoretical framework developed herein is substantiated by kinetic Monte Carlo growth simulations. Our findings highlight the possibility of using atomistic nucleation theory for pulsed vapor deposition to control morphology of thin films beyond the point of island density saturation. (C) 2015 AIP Publishing LLC.

  • 35.
    Münger, Peter
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Greene, Joseph E
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Sundgren, J E
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Adatom-induced diffusion of two-dimensional close-packed Pt-7 clusters on Pt(111)1996Inngår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 355, nr 1-3, s. L325-L330Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molecular dynamics simulations were used to follow the dynamics of the motion of hexagonal Pt heptamers on Pt(111). Close packed Pt-7 clusters on fee sites were found to be very stable structures with reconfiguration or translation events occurring only rarely over simulation times >30 ns at 1000 K. The adsorption of a single adatom on the cluster surface, however, induced rapid intracluster bond breaking, reconfiguration, the introduction of stacking faults, and greatly enhanced cluster diffusion rates. Cluster migration occurred primarily through sequences of individual atom and concerted dimer jumps, but concerted cluster motion was also observed. The adatoms eventually descended to the terrace, predominantly through push-out/exchange reactions with cluster atoms at B edges.

  • 36.
    Münger, Peter
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Hultman, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Greene, J.E.
    Adatom/vacancy interactions and interlayer mass transport in small two-dimensional Pt clusters on Pt(1 1 1)2003Inngår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 539, nr 1-3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use embedded-atom molecular dynamics simulations to follow the dynamics of adatoms, vacancies, and adatom/vacancy pairs on two-dimensional hexagonal Pt19 clusters on Pt(1 1 1) surfaces at 1000 K. All configurations are found to be quite stable and have essentially the same migration mobilities as compact hexagonal clusters. However, the presence of a single vacancy dramatically decreases the lifetime of an adatom on the cluster by a factor of three. This occurs primarily through an enhancement of the rate of push-out/exchange reactions at the outer cluster edge resulting from vacancy-induced softening of edge atom bonds. Overall, adatoms in the presence of vacancies descend to the terrace via vacancy filling 10% of the time, and through reactions with outer cluster edges the remaining 90%. Direct vacancy filling mechanisms are analogous to, and have similar activation energies with, those at outer cluster edges: adatom hopping over descending steps and push-out/exchange reactions. © 2003 Elsevier B.V. All rights reserved.

  • 37.
    Münger, Peter
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Sundgren, J E
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Greene, Joseph E
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Destabilization and diffusion of two-dimensional close-packed Pt clusters on Pt(111) during film growth from the vapor phase1998Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 318, nr 1-2, s. 57-60Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cluster migration is known to be an important process during film growth at elevated temperatures, but relatively little quantitative data is available. We have used molecular dynamics simulations to follow the dynamics of small two-dimensional Pt clusters on Pt(lll) at 1000 K. While close-packed Pt-7 heptamers are extremely stable structures, the addition of a single-cluster vacancy or an on-top adatom immediately results in intracluster bond breaking, reconfigurations, rotations, the introduction of stacking faults, and greatly enhanced cluster-diffusion rates. Mapping center-of-mass motion for total simulation times > 145 ns revealed increases in cluster velocities by more than an order of magnitude with cluster migration occurring primarily by concerted motion and a novel diffusion mechanism involving double shearing of dimers/trimers. Contrary to some previous reports, edge-atom diffusion plays only a minor role. (C) 1998 Elsevier Science S.A.

  • 38.
    Münger, Peter
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    NOVOTNY, MA
    Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida .
    MOMENTUM-SPACE MONTE-CARLO RENORMALIZATION-GROUP PROCEDURE1991Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 44, nr 9, s. 4314-4325Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We implement a momentum-space renormalization-group procedure into the Monte Carlo renormalization-group (MCRG) method. Usually the symmetries of the system must be known and incorporated into the renormalization group, but here we let the renormalization group be given by the Monte Carlo simulation itself This allows the MCRG method to be applicable to systems where the underlying symmetries may not be known, such as in Monte Carlo studies of quantum systems. As a test of this method, we apply it to the study of the two-dimensional square-lattice q-state Potts model, both for integer values of q and for noninteger values of q near q = 4.

  • 39.
    Münger, Peter
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    NOVOTNY, MA
    Supercomputer Computations Research Institute, Florida State University, Florida, USA .
    REWEIGHTING IN MONTE-CARLO AND MONTE-CARLO RENORMALIZATION-GROUP STUDIES1991Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 43, nr 7, B, s. 5773-5783Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method of reweighting Monte Carlo data to parameters other than the simulated ones is investigated. The method is also extended to include Monte Carlo renormalization-group simulations. Both single and multiple simulation reweighting is used. The models studied are the d = 2 ferromagnetic q = 3 Potts model and the d = 2 antiferromagnetic Ising model. It is shown that the reweighting produces a systematic shift in the height and location of the specific-heat peak. This shift, which without proper care may lead to erroneous results, depends on the simulated and reweighted temperatures and on the number of configurations included in the reweighting. Only for very large numbers of configurations does the shift decrease as the inverse square root of the number of configurations. Within the Monte Carlo renormalization-group study, it is shown that the critical exponents for the Ising model are determined more accurately from a multiple reweighting using one simulation below the critical temperature and one above than from the individual simulations. It is shown that it is more efficient to use two simulations at a time than all of them at once when reweighting multiple simulations.

  • 40.
    Silverå Ejneby, Malin
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelning för neurobiologi. Linköpings universitet, Medicinska fakulteten.
    Wu, Xiongyu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Ottosson, Nina
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelning för neurobiologi. Linköpings universitet, Medicinska fakulteten.
    Münger, E Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Lundström, Ingemar
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Konradsson, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Elinder, Fredrik
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelning för neurobiologi. Linköpings universitet, Medicinska fakulteten.
    Atom-by-atom tuning of the electrostatic potassium-channel modulator dehydroabietic acid2018Inngår i: The Journal of General Physiology, ISSN 0022-1295, E-ISSN 1540-7748, Vol. 150, nr 5, s. 731-750Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dehydroabietic acid (DHAA) is a naturally occurring component of pine resin that was recently shown to open voltage-gated potassium (KV) channels. The hydrophobic part of DHAA anchors the compound near the channel’s positively charged voltage sensor in a pocket between the channel and the lipid membrane. The negatively charged carboxyl group exerts an electrostatic effect on the channel’s voltage sensor, leading to the channel opening. In this study, we show that the channel-opening effect increases as the length of the carboxyl-group stalk is extended until a critical length of three atoms is reached. Longer stalks render the compounds noneffective. This critical distance is consistent with a simple electrostatic model in which the charge location depends on the stalk length. By combining an effective anchor with the optimal stalk length, we create a compound that opens the human KV7.2/7.3 (M type) potassium channel at a concentration of 1 µM. These results suggest that a stalk between the anchor and the effector group is a powerful way of increasing the potency of a channel-opening drug.

  • 41.
    Svedberg, E B
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Birch, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ivanov, Ivan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Sundgren, Jan- Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Asymmetric interface broadening in epitaxial Mo/W (001) superlattices grown by magnetron sputtering1998Inngår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 16, nr 2, s. 633-638Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interfacial structure in epitaxial Mo/W(001) superlattices, grown by magnetron sputtering on MgO(001) substrates has been studied. The films were grown in Ar and Kr discharges at a substrate temperature of 700 degrees C, and the as-deposited samples were analyzed by x-ray diffraction and found to be epitaxial with no high-angle grain boundaries. The degree of interfacial intermixing, caused by fluxes of different energetic species impinging on the growth surface, was estimated using a combination of Monte Carlo binary collision computer codes and a gas scattering computational model. In the Ar discharge case, large asymmetries in the Mo/W and W/Mo interfaces were found, with the W/Mo interface being more than a factor of 2 broader than the Mo/W interface. Simulations of x-ray reflectivity curves using the calculated interface profiles as input parameters without any additional fitting parameters agreed very well with measured data. The overall good fit between the calculated and measured reflectivity curves using the calculated compositional profiles is an indicator that the growth simulations using TRIM based codes provides interface profiles that are reasonably accurate, which can be used as a starting point for further refinements of the details of the interface structures. (C) 1998 American Vacuum Society.

  • 42.
    Tal, Alexey
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. National University of Science and Technology MISIS, Russia.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Abrikosov, Igor
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. National University of Science and Technology MISIS, Russia.
    Morphology transition mechanism from icosahedral to decahedral phase during growth of Cu nanoclusters2015Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, nr 2, s. 020102-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The morphology transition from the thermodynamically favorable to the unfavorable phase during growth of freestanding copper nanoclusters is studied by molecular dynamics simulations. We give a detailed description of the kinetics and thermodynamics of the process. A universal mechanism of a solid-solid transition, from icosahedral to decahedral morphology in the nanoclusters, is proposed. We show that a formation of distorted NC during the growth process with islands of incoming atoms localized in certain parts of the grown particle may shift the energy balance between Ih and Dh phases in favor of the latter leading to the morphology transition deep within the thermodynamic stability field of the former. The role of diffusion in the morphology transition is revealed. In particular, it is shown that fast diffusion should suppress the morphology transition and favor homogeneous growth of the nanoclusters.

  • 43.
    Tal, Alexey
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Abrikosov, Igor
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Brenning, Nils
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Pilch, Iris
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Molecular dynamics simulation of the growth of Cu nanoclusters from Cu ions in a plasma2014Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, nr 16, s. 165421-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A recently developed method of nanoclusters growth in a pulsed plasma is studied by means of molecular dynamics. A model that allows one to consider high-energy charged particles in classical molecular dynamics is suggested, and applied for studies of single impact events in nanoclusters growth. In particular, we provide a comparative analysis of the well-studied inert gas aggregation method and the growth from ions in a plasma. The importance to consider of the angular distribution of incoming ions in the simulations of the nanocluster growth is underlined. A detailed study of the energy transfer from the incoming ions to a nanocluster, as well as the diffusion of incoming ions on the cluster surface, is carried out. Our results are important for understanding and control of the nanocluster growth process.

  • 44.
    Wallin, Erik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Andersson, Jon Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, E. Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Ab initio studies of Al, O, and O2 adsorption on α-Al2O3 (0001) surfaces2006Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, nr 12, s. 125409-1-125409-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interactions of Al, O, and O2 with different α- Al2O3 (0001) surfaces have been studied using ab initio density functional theory methods. All three surface terminations obtainable by cleaving the bulk structure [single Al-layer (AlO), double Al-layer (AlAl), and O terminations] have been considered, as well as a completely hydrogenated O-terminated surface. Adsorbed Al shows strong ioniclike interaction with the AlO - and O-terminated surfaces, and several metastable adsorption sites are identified on the O-terminated surface. On the completely hydrogenated surface, however, Al adsorption in the bulk position is found to be unstable or very weak for the studied configurations of surface H atoms. Atomic O is found to interact strongly with the AlAl -terminated surface, where also O2 dissociative adsorption without any appreciable barrier is observed. In contrast, O adsorption on the AlO -terminated surface is metastable relative to molecular O2. On the O-terminated surface, we find the creation of O surface vacancies to be plausible, especially upon exposure to atomic O at elevated temperatures. The results are mainly discussed in the context of alumina thin film growth and provide insight into phenomena related to, e.g., preferred adsorption sites and effects of hydrogen on the growth.

  • 45.
    Wallin, Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik.
    Andersson, Jon
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik.
    Münger, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Chirita, Valeriu
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Helmersson, Ulf
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik.
    Ab initio studies of adsorption and diffusion processes on alpha-Al2O3 (0001) surfaces2007Inngår i: AVS 54th International Symposium,2007, 2007Konferansepaper (Annet vitenskapelig)
  • 46.
    Wallin, Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik.
    Andersson, Jon
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik.
    Münger, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Chirita, Valeriu
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Helmersson, Ulf
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik.
    Ab initio studies of adsorption and diffusion processes on alpha-Al2O3 (0001) surfaces2007Inngår i: International Symposium on Reactive Sputter Deposition,2007, 2007Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    As one of the technologically most important ceramic materials, alumina (Al2O3) thin film growth has been studied extensively in the past. However, the mechanisms behind the formation of different phases and microstructures are still poorly understood, especially for physically vapor deposited films. An increased atomic scale understanding of alumina surface processes would thus be an important step towards a more complete understanding and control of the deposition process. In the present work, density functional theory based methods were used to study the adsorption of Al, O, AlO, and O2 on different terminations of alpha-alumina (0001) surfaces. The results show the existence of several metastable adsorption sites on the O-terminated surface and provide a possible explanation for the well-known difficulties in growing -Ñ-alumina at lower temperatures. Moreover, we demonstrate that Al adsorption in bulk positions is unstable, or considerably weaker, for completely hydrogenated surfaces, indicating that hydrogen stemming from residues in vacuum systems, might hinder the growth of crystalline alpha-alumina. Furthermore, nudged elastic band investigations of dynamic energy barriers for different surface diffusion processes show that Al diffusion, on the Al-terminated (0001) surface, requires only ~0.7 eV. This value is considerably lower than what is generally expected for the low temperature synthesis of alpha-alumina phase. These results add significantly to understanding the effects of several important factors on alumina growth, and their implication, on optimizing deposition processes for the synthesis of alumina films with desired properties, will be discussed.

  • 47.
    Wallin, Erik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Chirita, Valeriu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Low-temperature alpha-alumina thin film growth: ab initio studies of Al adatom surface migration2009Inngår i: JOURNAL OF PHYSICS D-APPLIED PHYSICS, ISSN 0022-3727, Vol. 42, nr 12, s. 125302-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Investigations of activation energy barriers for Al surface hopping on alpha-Al2O3 (0 0 0 1) surfaces have been carried out by means of first-principles density functional theory calculations and the nudged elastic band method. Results show that surface diffusion on the (most stable) Al-terminated surface is relatively fast with an energy barrier of 0.75 eV, whereas Al hopping on the O-terminated surface is slower, with barriers for jumps from the two metastable positions existing on this surface to the stable site of 0.31 and 0.99 eV. Based on this study and on the literature, the governing mechanisms during low-temperature alpha-alumina thin film growth are summarized and discussed. Our results support suggestions made in some previous experimental studies, pointing out that limited surface diffusivity is not the main obstacle for alpha-alumina growth at low-to-moderate temperatures, and that other effects should primarily be considered when designing novel processes for low-temperature alpha-alumina deposition.

  • 48.
    Wang, Xin
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Madsen, Lynnette D
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Ivanov, Ivan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Rudner, Staffan
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Hjörvarsson, B
    Department of Physics, Uppsala University, Sweden.
    Sundgren, Jan-Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Composition, structure, and dielectric tunability of epitaxial SrTiO3 thin films grown by radio frequency magnetron sputtering1999Inngår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 17, nr 2, s. 564-570Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Epitaxial (001) oriented SrTiO3 films have been deposited on LaAlO3(001) substrates by off-axis radio frequency magnetron sputtering in Ar:O-2 gas mixtures at substrate temperatures ranging from 650 to 850 degrees C. For the deposition conditions used, stoichiometric targets yielded 20% Sr-deficient films, whereas Sr-enriched targets (Sr1.1TiO0.9O3.0) resulted in stoichiometric films. The Sr-deficient films had a mosaic structure and a larger lattice parameter in comparison to bulk SrTiO3. The stoichiometric films on the other hand had a much higher crystalline quality in the as-deposited condition. The mosaicity of the latter films was primarily limited by the crystalline quality of the LaAlO3 substrates. The lattice parameters of the stoichiometric films were also smaller than the Sr-deficient ones and closer to the bulk value. The dielectric properties of the stoichiometric films were superior to the Sr-deficient films. For films with a thickness of similar to 300 nm, the typical dielectric constants as measured at similar to 77 K and I MHz were determined to be 820 and 500, for the stoichiometric and Sr-deficient films, respectively. Also the capacitance change, as a direct current bias voltage was applied to an interdigital capacitor, was higher for the stoichiometric film, 27.3% as compared to 8.6% when applying a bias of 300 V at 77 K. We also demonstrate the effectiveness of thermal annealing in improving both crystalline quality and dielectric properties, especially for the Sr-deficient films. (C) 1999 American Vacuum Society. [S0734-2101(99)010002-7].

  • 49.
    Westwood, Luke
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Kaneryd, Linda
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Ebenman, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska högskolan.
    Keystone patches: upholding diversity in multi-trophic metacommunitiesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Due to the destruction of their habitat some organisms have an uneven distribution across the landscape. In affected areas a community of interacting organisms may be fragmented into a network of smaller patches connected through dispersal of individuals of the different species. These metacommunities can be modelled with explicit dynamics and spatial structure, with dependence on both local processes (interactions between species within a patch) and global processes (dispersal of individuals between patches). Dispersal between patches is important for the operation of processes like recolonizations and ‘rescue effects’, processes which can counteract local extinctions and hence reduce the risk of global extinctions. Recent studies have applied network theory to real ecological communities, with a wide selection of indices available to characterise either an individual patch or the whole patch network. Certain keystone patches may be the most important in upholding the local or global diversity of a metacommunity and may then be identified by such a network index. A range of network indices were calculated for the patches in a large set of simulated metacommunities and all of the indices identified the keystone patch quality to a certain degree. Some of the indices were consistently better than the others and the dependence of the keystone quality on these indices was at least two times larger than for the others. The quality identified by the indices was of being more important for upholding local rather than global diversity. Many parameters were varied between the different metacommunities and as a result of this the models for identifying keystone patches yielded small R2 values and therefore were not proven to be dependable predictors if applied to particular metacommunities.

1 - 49 of 49
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