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An ultraviolet photoemission study of H2O adsorption on Nb(110)
A604 Surface Science 292 (1993) 67-82 North-Holland
Backscattering of electrons in photoionization of an adsorbed CO molecule P. B u d a u 1, M. Buchner and (3 Ra§eev * Laboratotre de Photophysutue Moldcula~re * *, CNRS, B~nment 213, 91405 Orsay, France * * Received 15 December 1992, accepted for publication 26 Aprd 1993 A simple physical model, based on a step potential, is developed to study the backscattermg of electrons from photolomzatlon of adsorbed molecules on surfaces We used a two-step approach first, the calculation of photoiomzatlon of oriented-m-space molecules, second, the introduction of backscattenng as an a postenon correchon The three valence shell ionmaUon channels (5¢r)-l, (l~r)-1 and (4or)-I were calculated m the case of CO adsorbed on a N l ( l l l ) metalhc surface Backscattenng drastically changes the (5~r) - I shape resonance but It is not sufficient to explam the discrepancy between theory and experiment Chemlsorptlon, continuum-continuum interaction a n d / o r autolomzatlon and breaking of the araal symmetry should be responsible for this disagreement The (4~r)-1 shape resonance favorably compares with the experiment The relatmn between the backscattermg and circular dtchrolsm is also consldered
Surface Science 292 (1993) 83-97 North-Holland
Monte Carlo simulation of the transport of fast electrons and positrons in solids Kjeld O. Jensen a,b and Ahson B. Walker a a School of Phystcs, Unwerstty of East Angha, Norwtch, NR4 7TJ, UK b Department of Physics, Unwersity of Western Ontarw, London, Ontario N6A 3K7, Canada Received 13 January 1993, accepted for pubhcatlon 8 April 1993 We give a detailed description of a Monte Carlo simulation method for the transport of high energy (1-50 keV) positrons and electrons m solids using either the Penn dielectric loss function or the l_andhard dielectric function to model inelastic scattenng and elastic scattering cross sections obtained from a partml wave expansion Results for positron ~mplantat~on and baekscattermg for Be, AI, Cu, Ag and Au are presented Simulation results and experiments for positrons are found to be m very good agreement, which confirms the accuracy of the Penn model for describing inelastic seattenng of positrons m sohds In the case of electrons agreement between simulated and experimental backscattermg probabdlttes Is reasonable but there are slgmficant discrepancies which can be explained by the neglect of the mdlstmgmshabdlty of electrons m the Penn model
Surface Science 292 (1993) 98-113 North-Holland
Synchronization of nucleation studied with Monte Carlo simulations and applied to S i l _ x G e x molecular beam epitaxy Mats I. Larsson * and Gdran V. Hansson Department of Phystcs, Lmkopmg lnstttute of Technology, S-581 83 Lmkopmg, Sweden Received 29 January 1993, accepted for pubhcatlon 19 April 1993 The method of synchromzaUon of nucleation (SN) by means of periodically altering the substrate temperature has been studied by using a smaple Monte Carlo simulation model The growth smaulatlons were performed on a Sl(100)-type geometry Both an ideal sawtooth-shaped substrate temperature function and a reahstlc temperature function, which is vahd for an indirectly heated substrate, were apphod The results from the simulations with the reahstlc temperature modulalaon correspond quahtatrvely to previously reported experimental data for homoepltaJoal growth of S! on Si(lll) and Ge on G e ( l l l ) using SN We predict that correctly apphed SN should also Improve the 2D character of Sl on $1(100) epztaxy Finally, experimental results on SN applied to heteroepltaxml growth of Sl~_xGex are presented
Backscattering of electrons in photoionization of an adsorbed CO molecule P. B u d a u 1, M. Buchner and (3 Ra§eev * Laboratotre de Photophysutue Moldcula~re * *, CNRS, B~nment 213, 91405 Orsay, France * * Received 15 December 1992, accepted for publication 26 Aprd 1993 A simple physical model, based on a step potential, is developed to study the backscattermg of electrons from photolomzatlon of adsorbed molecules on surfaces We used a two-step approach first, the calculation of photoiomzatlon of oriented-m-space molecules, second, the introduction of backscattenng as an a postenon correchon The three valence shell ionmaUon channels (5¢r)-l, (l~r)-1 and (4or)-I were calculated m the case of CO adsorbed on a N l ( l l l ) metalhc surface Backscattenng drastically changes the (5~r) - I shape resonance but It is not sufficient to explam the discrepancy between theory and experiment Chemlsorptlon, continuum-continuum interaction a n d / o r autolomzatlon and breaking of the araal symmetry should be responsible for this disagreement The (4~r)-1 shape resonance favorably compares with the experiment The relatmn between the backscattermg and circular dtchrolsm is also consldered
Surface Science 292 (1993) 83-97 North-Holland
Monte Carlo simulation of the transport of fast electrons and positrons in solids Kjeld O. Jensen a,b and Ahson B. Walker a a School of Phystcs, Unwerstty of East Angha, Norwtch, NR4 7TJ, UK b Department of Physics, Unwersity of Western Ontarw, London, Ontario N6A 3K7, Canada Received 13 January 1993, accepted for pubhcatlon 8 April 1993 We give a detailed description of a Monte Carlo simulation method for the transport of high energy (1-50 keV) positrons and electrons m solids using either the Penn dielectric loss function or the l_andhard dielectric function to model inelastic scattenng and elastic scattering cross sections obtained from a partml wave expansion Results for positron ~mplantat~on and baekscattermg for Be, AI, Cu, Ag and Au are presented Simulation results and experiments for positrons are found to be m very good agreement, which confirms the accuracy of the Penn model for describing inelastic seattenng of positrons m sohds In the case of electrons agreement between simulated and experimental backscattermg probabdlttes Is reasonable but there are slgmficant discrepancies which can be explained by the neglect of the mdlstmgmshabdlty of electrons m the Penn model
Surface Science 292 (1993) 98-113 North-Holland
Synchronization of nucleation studied with Monte Carlo simulations and applied to S i l _ x G e x molecular beam epitaxy Mats I. Larsson * and Gdran V. Hansson Department of Phystcs, Lmkopmg lnstttute of Technology, S-581 83 Lmkopmg, Sweden Received 29 January 1993, accepted for pubhcatlon 19 April 1993 The method of synchromzaUon of nucleation (SN) by means of periodically altering the substrate temperature has been studied by using a smaple Monte Carlo simulation model The growth smaulatlons were performed on a Sl(100)-type geometry Both an ideal sawtooth-shaped substrate temperature function and a reahstlc temperature function, which is vahd for an indirectly heated substrate, were apphod The results from the simulations with the reahstlc temperature modulalaon correspond quahtatrvely to previously reported experimental data for homoepltaJoal growth of S! on Si(lll) and Ge on G e ( l l l ) using SN We predict that correctly apphed SN should also Improve the 2D character of Sl on $1(100) epztaxy Finally, experimental results on SN applied to heteroepltaxml growth of Sl~_xGex are presented