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Properties and influence of surface defects
A332 Surface Science 251/252 ( 1991 ) 383- 386 N orth-Holland
Observation of discrete energy loss peaks in grazing-angle scattering of protons from a graphite surface F. StiSlzle and R. Pfandzelter Sektion Physik, Unwersitiit Miinchen, Amalienstrasse 54, W-8000 Mi~nchen 40, Germar(v Received 1 October 1990: accepted for publication 23 November 1990 We have measured the energy spectra of specularly reflected protons obtained from a 15-75 keV proton beam g r ~ i n g l y incident upon a smooth polycrystalline graphite surface. The energy spectra exhibit several discrete energy loss peaks, separated by nearly equal energy spacings. The energy loss of the main peak decreases monotoneously with increasing incidence angle, This is m agreement with a computer simulation, if the dynamical image potential is taken into account. Possible explanations for the multiple peak structure of the energy spectra are briefly discussed.
Surface Science 251/252 (1991) 387-395 North-Holland
387
Properties and influence of surface defects Klaus Wandelt lnstitut fiir Physikalische und Theoretische Chemie, Universitiit Bonn, Wegelerstrasse 12, 5300 Bonn 1, Germany Received 20 February 1991; accepted for publication 1 March 1991 With a few examples the present paper underlines the dramatic influence of atomic scale surface defects on surface processes such as sticking, heterogeneous catalysis, film growth and surface reactions on the one hand as well as the local nature of the structural, vibrational and electronic properties of the defects on the other hand. Since the latter are widely unknown, but some techniques of the necessary resolution are available now, the paper is a call for more systematic investigations on the local properties of surface defects on an atomic scale in order to fathom the ultimate physical reasons for their influence on the above-mentioned and other surface processes.
396
Surface Science 251/252 (1991) 396-400 North-Holland
Optical response of Si(lll)-7 × 7 R. Alameh and Y. Borensztein Laboratoire d'Optique des Solides, UA C N R S 781, UniversitO Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France Received 1 October 1990; accepted for publication 15 January 1991 The optical properties of the Si(lll)-7 × 7 surface are studied by means of a surface differential reflectometer. The optical reflectivity of the clean surface is first compared to that of the native oxide-covered Si surface, then to that of the oxygen-exposed surface. The exact surface optical response function of the Si(lll)-7 × 7 surface and its changes upon adsorption of oxygen are determined by use of an electromagnetic surface model. A main peak is observed at 3.9 eV and is interpreted as due to electronic transitions from the back-bond states of the Si adatoms to a bulk conduction band. Secondary maxima at lower energies, due to transitions involving the dangling bond states, are also observed. Indications on the oxygen chemisorption mode are finally deduced.
Observation of discrete energy loss peaks in grazing-angle scattering of protons from a graphite surface F. StiSlzle and R. Pfandzelter Sektion Physik, Unwersitiit Miinchen, Amalienstrasse 54, W-8000 Mi~nchen 40, Germar(v Received 1 October 1990: accepted for publication 23 November 1990 We have measured the energy spectra of specularly reflected protons obtained from a 15-75 keV proton beam g r ~ i n g l y incident upon a smooth polycrystalline graphite surface. The energy spectra exhibit several discrete energy loss peaks, separated by nearly equal energy spacings. The energy loss of the main peak decreases monotoneously with increasing incidence angle, This is m agreement with a computer simulation, if the dynamical image potential is taken into account. Possible explanations for the multiple peak structure of the energy spectra are briefly discussed.
Surface Science 251/252 (1991) 387-395 North-Holland
387
Properties and influence of surface defects Klaus Wandelt lnstitut fiir Physikalische und Theoretische Chemie, Universitiit Bonn, Wegelerstrasse 12, 5300 Bonn 1, Germany Received 20 February 1991; accepted for publication 1 March 1991 With a few examples the present paper underlines the dramatic influence of atomic scale surface defects on surface processes such as sticking, heterogeneous catalysis, film growth and surface reactions on the one hand as well as the local nature of the structural, vibrational and electronic properties of the defects on the other hand. Since the latter are widely unknown, but some techniques of the necessary resolution are available now, the paper is a call for more systematic investigations on the local properties of surface defects on an atomic scale in order to fathom the ultimate physical reasons for their influence on the above-mentioned and other surface processes.
396
Surface Science 251/252 (1991) 396-400 North-Holland
Optical response of Si(lll)-7 × 7 R. Alameh and Y. Borensztein Laboratoire d'Optique des Solides, UA C N R S 781, UniversitO Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France Received 1 October 1990; accepted for publication 15 January 1991 The optical properties of the Si(lll)-7 × 7 surface are studied by means of a surface differential reflectometer. The optical reflectivity of the clean surface is first compared to that of the native oxide-covered Si surface, then to that of the oxygen-exposed surface. The exact surface optical response function of the Si(lll)-7 × 7 surface and its changes upon adsorption of oxygen are determined by use of an electromagnetic surface model. A main peak is observed at 3.9 eV and is interpreted as due to electronic transitions from the back-bond states of the Si adatoms to a bulk conduction band. Secondary maxima at lower energies, due to transitions involving the dangling bond states, are also observed. Indications on the oxygen chemisorption mode are finally deduced.