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Theoretical study of the electronic structure of the dimer-adatom-stacking-fault model for the Si(111) surface
A634 Surface Science 259 (1991) 323-338 North-Holland
Steps on Si(001) vicinal surfaces tilted by various angles in the [110]-, [100]- and [210]-zones, investigated by high-resolution LEED E. Schr6der-Bergen and W. Ranke Fritz-Haber-lnstitut der Max-Planck-Gesellschaft, Faradayweg4-6, D-1000 Berlin 33, Germany Received 25 March 1991; accepted for publication 9 July 1991 The kind and distribution of atomic steps in the vicinity of Si(001), clean and after exposure to water, was investigated by high-resolution spot-profile-analysis LEED. The sample was spherically shaped with Si(001) in its center so that a continuous tilt angle range 0 ° _< 3' -< 13.5 ° was accessible. In the [ll0]-zone, single layer steps are found with a tendency for step pairing with narrower A- and wider B-terraces. Beyond -), = 1.5 °, the A-terrace width locally becomes zero so that paired single steps and true Dl~-type double steps coexist, probably stabilized by kinks. Kinked Dn-steps cause a correlated lateral shift of dimer rows across steps. Only beyond y = 8 °, the clean surface is completely Dt~-stepped. Water adsorption reduces the pairing tendency. The pairing mechanism is based on the different contribution of S A- and SB-type single steps to surface strain. A mean terrace inclination decreasing with increasing terrace width is observed which is compatible with a constant edge depression. For 3' > 9 °, the special stability of the (117) orientation causes separation into (117) facets (3, = 11.4 ° ) and less tilted stepped domains. The step topography is similar in the [210]-zone. The steps there can be considered as strongly kinked [ll0]-type steps. In the [10(I]-zone, only single steps without pairing are observed up to y = 6 ° which agrees with the equivalency of both sublattices with respect to the edge direction.
Surface Science 259 (1991) 339-350 North-Holland
Theory of scanning tunneling spectroscopy: application to Si(100)2 × 1 surface S.N. Molotkov, S.S. Nazin, I.S. Smirnova and V.V. Tatarskii Institute of Solid State Physics, 142432 Chernogolovka, Moscow District, USSR Received 1 April 1991; accepted for publication 4 July 1991 Presented is the theory of scanning tunneling microscopy (STM) based on the quasistationary states approach. The tunneling current is calculated as a sum of quasistationary states decay rates. This method naturally takes into account the atomic structure of the tip and crystal surfaces as well as their mutual influence. In the weak tip-to-crystal coupling limit our expression for the tunneling current reduces to that derived in the B a r d e e n - T e r s o f f - H a m a n n method. Tunneling current relief, I-V characteristics and tunneling density of states for the Si(100)2 × 1 surface have been calculated and compared with experimental results.
Surface Science 259 (1991) 351-358 North-Holland
Theoretical study of the electronic structure of the dimer-adatom-stacking-fault model for the Si(lll) surface Mari Fujita Department of Material Physics, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560, Japan
Hideo Nagayoshi Department of Physics, Faculty of Science, Kagoshima Unit,ersity, Kagoshima 890, Japan
and
A635 Akio Yoshimori t Department of Material Physics, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560, Japan Received 2 May 1991; accepted for publication 26 June 1991 The electronic structure of the Si(lll)7 × 7 dimer-adatom-stacking-fault (DAS) model has been calculated in the slab geometry, using the local density approximation (LDA) and the norm-conserving pseudopotential. Surface states and resonance states are obtained in the whole energy range for valence electrons. The dependence of one-electron energies on the cut-off values in the plane wave expansion is examined for the 1 × 1 truncated surface, and the result is utilized for the interpretation of the calculated result of the 7 x 7 surface. The obtained results for the 7 x 7 DAS model are found to agree well with the experimental ones for the 7 x 7 reconstructed surface.
Surface Science 259 (1991) 359-370 North-Holland
Scattering of energetic beams at glancing incidence from crystal surfaces: a molecular dynamics simulation D. Danailov t, J.-H. Rechtien and K.J. Snowdon Fachbereich Physik, Universitiit Osnabriick, Postfach 4469, D-4500 Osnabriick, Germany Received 28 March 1991; accepted for publication 8 July 1991 The elastic scattering of keV atomic beams of He and Xe incident at grazing angles to a C u ( l l l ) surface is investigated within a classical molecular dynamics formalism. We find that only the corrugation of the interaction potential in the surface direction perpendicular to the incident beam direction significantly influences the scattering, and then only for incidence of the beam along low index crystallographic directions. This corrugation component leads to rainbow scattering in the out of plane angular distribution. The influence of the thermal motion of the surface atoms is two-fold. The thermal displacement component perpendicular to the surface (and only this component) has a significant influence on the energy and angular straggling of both beams. The thermal velocity significantly influences the energy straggling of light projectiles. We find a positive correlation between energy loss and deflection angle of the beam. We show that surface scattering under grazing incidence conditions of keV atomic beams along high index crystallographic directions on close packed surfaces may indeed be accurately simulated (for a restricted range of incident beam energies and incidence angles) using one-dimensional (planar) potentials.
Surface Science 259 (1991) 371-388 North-Holland
A molecular dynamics study of a nearly incommensurate overlayer on a metal substrate J.E. Black, A. Janzen Brock Uniuersity, St. Catharines, Ontario, Canada L2S 3.41
and P. Bopp lnstitut fiir Physikalische Chemie, Rheinisch-Westfaelische Technische Hochschule, Templegrabe 59, D-5100 Aachen, Germany Received 8 June 1991; accepted for publication 2 July 1991 We have examined the dynamics of a nearly incommensurate metal overlayer on a metal substrate using the technique of molecular dynamics. We have chosen the parameters in our model of the interatomic forces between atoms to fit the experimentally observed perpendicular vibration frequency of a silver overlayer on Ni(100). The corrugation of the silver-nickel interaction is not known. With this model it is possible to vary the corrugation of the adatom-substrate interaction potential. Thus we can study, in a general way, the effects of corrugation on the phonon spectrum and the dynamics of adatoms. At high temperatures (room temperature and above) we find the metal atoms undergo large displacements with respect to the substrate. The effects of these displacements on the phonon spectra are examined as a function of temperature and the corrugation of the interaction potential. The results will be of use to experimentalists studying the vibrations of nearly incommensurate systems.
Steps on Si(001) vicinal surfaces tilted by various angles in the [110]-, [100]- and [210]-zones, investigated by high-resolution LEED E. Schr6der-Bergen and W. Ranke Fritz-Haber-lnstitut der Max-Planck-Gesellschaft, Faradayweg4-6, D-1000 Berlin 33, Germany Received 25 March 1991; accepted for publication 9 July 1991 The kind and distribution of atomic steps in the vicinity of Si(001), clean and after exposure to water, was investigated by high-resolution spot-profile-analysis LEED. The sample was spherically shaped with Si(001) in its center so that a continuous tilt angle range 0 ° _< 3' -< 13.5 ° was accessible. In the [ll0]-zone, single layer steps are found with a tendency for step pairing with narrower A- and wider B-terraces. Beyond -), = 1.5 °, the A-terrace width locally becomes zero so that paired single steps and true Dl~-type double steps coexist, probably stabilized by kinks. Kinked Dn-steps cause a correlated lateral shift of dimer rows across steps. Only beyond y = 8 °, the clean surface is completely Dt~-stepped. Water adsorption reduces the pairing tendency. The pairing mechanism is based on the different contribution of S A- and SB-type single steps to surface strain. A mean terrace inclination decreasing with increasing terrace width is observed which is compatible with a constant edge depression. For 3' > 9 °, the special stability of the (117) orientation causes separation into (117) facets (3, = 11.4 ° ) and less tilted stepped domains. The step topography is similar in the [210]-zone. The steps there can be considered as strongly kinked [ll0]-type steps. In the [10(I]-zone, only single steps without pairing are observed up to y = 6 ° which agrees with the equivalency of both sublattices with respect to the edge direction.
Surface Science 259 (1991) 339-350 North-Holland
Theory of scanning tunneling spectroscopy: application to Si(100)2 × 1 surface S.N. Molotkov, S.S. Nazin, I.S. Smirnova and V.V. Tatarskii Institute of Solid State Physics, 142432 Chernogolovka, Moscow District, USSR Received 1 April 1991; accepted for publication 4 July 1991 Presented is the theory of scanning tunneling microscopy (STM) based on the quasistationary states approach. The tunneling current is calculated as a sum of quasistationary states decay rates. This method naturally takes into account the atomic structure of the tip and crystal surfaces as well as their mutual influence. In the weak tip-to-crystal coupling limit our expression for the tunneling current reduces to that derived in the B a r d e e n - T e r s o f f - H a m a n n method. Tunneling current relief, I-V characteristics and tunneling density of states for the Si(100)2 × 1 surface have been calculated and compared with experimental results.
Surface Science 259 (1991) 351-358 North-Holland
Theoretical study of the electronic structure of the dimer-adatom-stacking-fault model for the Si(lll) surface Mari Fujita Department of Material Physics, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560, Japan
Hideo Nagayoshi Department of Physics, Faculty of Science, Kagoshima Unit,ersity, Kagoshima 890, Japan
and
A635 Akio Yoshimori t Department of Material Physics, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560, Japan Received 2 May 1991; accepted for publication 26 June 1991 The electronic structure of the Si(lll)7 × 7 dimer-adatom-stacking-fault (DAS) model has been calculated in the slab geometry, using the local density approximation (LDA) and the norm-conserving pseudopotential. Surface states and resonance states are obtained in the whole energy range for valence electrons. The dependence of one-electron energies on the cut-off values in the plane wave expansion is examined for the 1 × 1 truncated surface, and the result is utilized for the interpretation of the calculated result of the 7 x 7 surface. The obtained results for the 7 x 7 DAS model are found to agree well with the experimental ones for the 7 x 7 reconstructed surface.
Surface Science 259 (1991) 359-370 North-Holland
Scattering of energetic beams at glancing incidence from crystal surfaces: a molecular dynamics simulation D. Danailov t, J.-H. Rechtien and K.J. Snowdon Fachbereich Physik, Universitiit Osnabriick, Postfach 4469, D-4500 Osnabriick, Germany Received 28 March 1991; accepted for publication 8 July 1991 The elastic scattering of keV atomic beams of He and Xe incident at grazing angles to a C u ( l l l ) surface is investigated within a classical molecular dynamics formalism. We find that only the corrugation of the interaction potential in the surface direction perpendicular to the incident beam direction significantly influences the scattering, and then only for incidence of the beam along low index crystallographic directions. This corrugation component leads to rainbow scattering in the out of plane angular distribution. The influence of the thermal motion of the surface atoms is two-fold. The thermal displacement component perpendicular to the surface (and only this component) has a significant influence on the energy and angular straggling of both beams. The thermal velocity significantly influences the energy straggling of light projectiles. We find a positive correlation between energy loss and deflection angle of the beam. We show that surface scattering under grazing incidence conditions of keV atomic beams along high index crystallographic directions on close packed surfaces may indeed be accurately simulated (for a restricted range of incident beam energies and incidence angles) using one-dimensional (planar) potentials.
Surface Science 259 (1991) 371-388 North-Holland
A molecular dynamics study of a nearly incommensurate overlayer on a metal substrate J.E. Black, A. Janzen Brock Uniuersity, St. Catharines, Ontario, Canada L2S 3.41
and P. Bopp lnstitut fiir Physikalische Chemie, Rheinisch-Westfaelische Technische Hochschule, Templegrabe 59, D-5100 Aachen, Germany Received 8 June 1991; accepted for publication 2 July 1991 We have examined the dynamics of a nearly incommensurate metal overlayer on a metal substrate using the technique of molecular dynamics. We have chosen the parameters in our model of the interatomic forces between atoms to fit the experimentally observed perpendicular vibration frequency of a silver overlayer on Ni(100). The corrugation of the silver-nickel interaction is not known. With this model it is possible to vary the corrugation of the adatom-substrate interaction potential. Thus we can study, in a general way, the effects of corrugation on the phonon spectrum and the dynamics of adatoms. At high temperatures (room temperature and above) we find the metal atoms undergo large displacements with respect to the substrate. The effects of these displacements on the phonon spectra are examined as a function of temperature and the corrugation of the interaction potential. The results will be of use to experimentalists studying the vibrations of nearly incommensurate systems.