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An effective procedure to determine corrugation functions from atomic beam-diffraction intensities
A262 Surface Science 108 (1981) 135-152 North-Holland Publishing Company
135
BULK AND SURFACE CHARACTERIZATION OF THE SILICON ELECTRODE * M.J. M A D O U , B.H. L O O , K.W. F R E S E and S. R o y M O R R I S O N SRl lnternational, Menlo Park, California 94025, USA Received 8 December 1980; accepted for publication 17 February 1981 The properties of silicon as an electrode are investigated. Techniques for reproducible measurement of the doping level are described, techniques designed to avoid surface films associated with fluoride ions. A peak in the capacity/voltage curve that appears near the flatband voltage for both n- and p-type silicon is characterized in detail and shown to be associated with interface states between a surface oxide layer and the silicon. The possible chemical origin of the interface states when the electrode is in solution is discussed.
Surface Science 108 (1981) 153-168 North-Holland Publishing Company
153
T H E A D S O R P T I O N O F H Y D R O G E N O N T H E (100) S U R F A C E S O F S I L I C O N AND DIAMOND W.S. V E R W O E R D * lnstitut fiir Theoretische Physik, Technische Universitdt Clausthal, D.3392 Clausthal-Zellerfeld, Federal Republic of Germany Received 28 October 1980; accepted for publication 26 January 1981
Energy and structural calculations of hydrogen interacting with 9-atom clusters modelling the (100) surfaces of silicon and diamond, using the MINDO/3 and MNDO semiempixical quantum chemistry procedures, are reported. The equilibrium structure of the monohydride phases are symmetric dimers with stretched dimer bond lengths (2.53 A for Si and 1.67 A for C). The dihydrides have bulk-like structures with the H layer raised about 20% relative to tetragonal layer separations. We show that the dimer bonds on the monohydride phases are unstable against corrosion by atomic hydrogen (in contrast to the back bonds) and that there is a large difference between the desorption energies of the two phases, in agreement with the observed difference in thermal desorption temperatures. Values are calculated for the work function changes on formation of both hydride phases.
Surface Science 108 (1981) 169-180 North-Holland Publishing Company
169
AN EFFECTIVE PROCEDURE TO DETERMINE CORRUGATION FUNCTIONS FROM ATOMIC BEAM-DIFFRACTION INTENSITIES K.H. R I E D E R IBM Zurich Research Laboratory, CH-8803 Riischlikon, Switzerland N. G A R C I A * Departamento de Fisica Fundamentale, Insfftuto dei Estado Solido, Universidad Autonoma de Madrid, Canto Blanco, E-Madrid 34, Spain and
A263 V. C E L L I Physics Department, University o f Virginia, Charlottesville, Virginia 22901, USA Received 15 October 1980; accepted for publication 15 January 1981
A computational method is described, which, starting from given difraction intensities, approaches effectively the best-fit corrugation function ~'(R). Because of the approximations involved, the procedure works well for smooth corrugations with amplitudes not exceeding ~ 10% of the lattice constant. The method rests on two crucial observations: (i) With the full knowledge of the scattering amplitudes A G = IA G I exp(i~0G) (absolute values plus phases), the corrugation function can be calculated to a high degree of accuracy from ~'(R) = (2iki) -1 lnl A G exp(iG .R) I which is derived easily from the hard corrugated wall scattering (HCWS) equation by approximating k G by - k i (k i and k G being the wavevectors of the incoming and diffracted beams, respectively). (ii) With only the IA G I's (or intensities) known, approximate solutions of the HCWS equation can be obtained with a rough estimate o f the relative phases o f only a f e w intense diffraction beams: the estimate is readily performed by investigating systematically a coarse mesh of phases. In this way, approximate corrugations are found with which a full set of phases can be generated, which allows the calculation of an improved ~'(R); this step is repeated in a loop, until optimum agreement between calculated and given intensities is obtained. The effectiveness of the procedure is demonstrated for three one-dimensional model corrugations described by several Fourier coefficients. The method is finally applied to the case of H2 diffraction from the quasi-one-dimensional adsorbate corrugation Ni(110) + H(1 x 2).
181
Surface Science 108 (1981) 181-204 North-Holland Publishing Company Q U A N T U M THEORY OF A T O M - S U R F A C E
SCATTERING:
COMMENSURATE ADSORBATES A.C. L E V I , R. S P A D A C I N I a n d G.E. T O M M E I Istituto di Scienze Fisiche dell 'Universit~ and Gruppo Nazionale di Struttura della Materia del CNR, Viale Benedetto XV, 5, 1-16132 Genova, Italy Received 27 June 1980; accepted for publication 28 January 1981
The general theory of atom scattering in the eikonal approximation, developed previously, is extended to commensurate adsorbates. In the case of elastic scattering coherent and incoherent contributions are evaluated. Special reference is made to two simple models: the independent site model and the island model, and the connection with two-dimensional phase transitions is briefly discussed. Calculations are presented for the examples of Kr/graphite andO/W(110). In the case of inelastic scattering the motion of the substrate is separated from the motion of an adsorbed atom, and the possibility of treating the latter as a set of Einstein oscillators is considered.
135
BULK AND SURFACE CHARACTERIZATION OF THE SILICON ELECTRODE * M.J. M A D O U , B.H. L O O , K.W. F R E S E and S. R o y M O R R I S O N SRl lnternational, Menlo Park, California 94025, USA Received 8 December 1980; accepted for publication 17 February 1981 The properties of silicon as an electrode are investigated. Techniques for reproducible measurement of the doping level are described, techniques designed to avoid surface films associated with fluoride ions. A peak in the capacity/voltage curve that appears near the flatband voltage for both n- and p-type silicon is characterized in detail and shown to be associated with interface states between a surface oxide layer and the silicon. The possible chemical origin of the interface states when the electrode is in solution is discussed.
Surface Science 108 (1981) 153-168 North-Holland Publishing Company
153
T H E A D S O R P T I O N O F H Y D R O G E N O N T H E (100) S U R F A C E S O F S I L I C O N AND DIAMOND W.S. V E R W O E R D * lnstitut fiir Theoretische Physik, Technische Universitdt Clausthal, D.3392 Clausthal-Zellerfeld, Federal Republic of Germany Received 28 October 1980; accepted for publication 26 January 1981
Energy and structural calculations of hydrogen interacting with 9-atom clusters modelling the (100) surfaces of silicon and diamond, using the MINDO/3 and MNDO semiempixical quantum chemistry procedures, are reported. The equilibrium structure of the monohydride phases are symmetric dimers with stretched dimer bond lengths (2.53 A for Si and 1.67 A for C). The dihydrides have bulk-like structures with the H layer raised about 20% relative to tetragonal layer separations. We show that the dimer bonds on the monohydride phases are unstable against corrosion by atomic hydrogen (in contrast to the back bonds) and that there is a large difference between the desorption energies of the two phases, in agreement with the observed difference in thermal desorption temperatures. Values are calculated for the work function changes on formation of both hydride phases.
Surface Science 108 (1981) 169-180 North-Holland Publishing Company
169
AN EFFECTIVE PROCEDURE TO DETERMINE CORRUGATION FUNCTIONS FROM ATOMIC BEAM-DIFFRACTION INTENSITIES K.H. R I E D E R IBM Zurich Research Laboratory, CH-8803 Riischlikon, Switzerland N. G A R C I A * Departamento de Fisica Fundamentale, Insfftuto dei Estado Solido, Universidad Autonoma de Madrid, Canto Blanco, E-Madrid 34, Spain and
A263 V. C E L L I Physics Department, University o f Virginia, Charlottesville, Virginia 22901, USA Received 15 October 1980; accepted for publication 15 January 1981
A computational method is described, which, starting from given difraction intensities, approaches effectively the best-fit corrugation function ~'(R). Because of the approximations involved, the procedure works well for smooth corrugations with amplitudes not exceeding ~ 10% of the lattice constant. The method rests on two crucial observations: (i) With the full knowledge of the scattering amplitudes A G = IA G I exp(i~0G) (absolute values plus phases), the corrugation function can be calculated to a high degree of accuracy from ~'(R) = (2iki) -1 lnl A G exp(iG .R) I which is derived easily from the hard corrugated wall scattering (HCWS) equation by approximating k G by - k i (k i and k G being the wavevectors of the incoming and diffracted beams, respectively). (ii) With only the IA G I's (or intensities) known, approximate solutions of the HCWS equation can be obtained with a rough estimate o f the relative phases o f only a f e w intense diffraction beams: the estimate is readily performed by investigating systematically a coarse mesh of phases. In this way, approximate corrugations are found with which a full set of phases can be generated, which allows the calculation of an improved ~'(R); this step is repeated in a loop, until optimum agreement between calculated and given intensities is obtained. The effectiveness of the procedure is demonstrated for three one-dimensional model corrugations described by several Fourier coefficients. The method is finally applied to the case of H2 diffraction from the quasi-one-dimensional adsorbate corrugation Ni(110) + H(1 x 2).
181
Surface Science 108 (1981) 181-204 North-Holland Publishing Company Q U A N T U M THEORY OF A T O M - S U R F A C E
SCATTERING:
COMMENSURATE ADSORBATES A.C. L E V I , R. S P A D A C I N I a n d G.E. T O M M E I Istituto di Scienze Fisiche dell 'Universit~ and Gruppo Nazionale di Struttura della Materia del CNR, Viale Benedetto XV, 5, 1-16132 Genova, Italy Received 27 June 1980; accepted for publication 28 January 1981
The general theory of atom scattering in the eikonal approximation, developed previously, is extended to commensurate adsorbates. In the case of elastic scattering coherent and incoherent contributions are evaluated. Special reference is made to two simple models: the independent site model and the island model, and the connection with two-dimensional phase transitions is briefly discussed. Calculations are presented for the examples of Kr/graphite andO/W(110). In the case of inelastic scattering the motion of the substrate is separated from the motion of an adsorbed atom, and the possibility of treating the latter as a set of Einstein oscillators is considered.