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The oxidation of nickel: A study of empty electronic states by inverse photoemission and soft X-ray appearance potential spectroscopy
A426 Surface Science 112 (1981) 97-110 North-Holland Publishing Company
97
THE OXIDATION OF NICKEL: A STUDY OF EMPTY ELECTRONIC STATES BY INVERSE PHOTOEMISSION AND SOFT X-RAY APPEARANCE POTENTIAL SPECTROSCOPY H. SCHEIDT,
M. GLOBL
a n d V. D O S E
Physikalisches lnstitut der Universiti~t, D-8700 Wi~rzburg, German), Received 5 June 1981; accepted for publication 29 July 1981 Soft X-ray appearance potential spectroscopy (SXAPS) and inverse photoemission (IPE) have been employed to study the oxidation of a polycrystalline nickel sample. Both methods probe empty electronic states. The present results when supplemented by UPS data establish an experimental determination of the NiO band structure consistent with theoretical models of localized and itinerant states.
Surface Science 112 (1981) 111-132 North-Holland Publishing Company SHADOWING, FOCUSSING AND CHARGE-EXCHANGE EFFECTS THE ANGULAR DISTRIBUTIONS OF keV Ne + AND H20 + IONS S C A ' I T E R E D F R O M Cu{ 110) II. T h e
111 IN
surface geometry of the first two layers
R.P.N. BRONCKERS
and A.G.J. DE WIT
Fysisch Laboratorium der Ri)ksuniversiteit Utrecht, Princetonplein 5, 3584 CC Utrecht, The Netherlands Received 4 December 1980; accepted for publication 17 June 1981 The structure of the first and second surface layer of a Cu{ 110} crystal is investigated with low energy (keV region) Ne + and H20 + scattering. The anisotropies in the intensity of scattered Ne + ions and O - ions are measured for various elevation angles of incidence and ejection. Similarities in these anisotropies can be explained by blocking and ion-focussing effects. Differences in the anisotropies are ascribed to charge-exchange processes. The intensities of scattered ions, plotted in a so-called photogram, reflect clearly the geometry of the atoms of the first and second layer. Consequently, photograms obtained with LEIS can be used for structure analysis of single crystalline surfaces. Relative large intensities in the distributions of O - ions scattered from the Cu(1 I0) surface are explained to be caused by effects of focussing the primary ions on atoms of the .second layer by atoms of the first layer. For low primary energies (1 keV) wedge-focussing in the semi-channels was found. Similar phenomena are observed for Ne + ion scattering, but here the effects are less pronounced.
97
THE OXIDATION OF NICKEL: A STUDY OF EMPTY ELECTRONIC STATES BY INVERSE PHOTOEMISSION AND SOFT X-RAY APPEARANCE POTENTIAL SPECTROSCOPY H. SCHEIDT,
M. GLOBL
a n d V. D O S E
Physikalisches lnstitut der Universiti~t, D-8700 Wi~rzburg, German), Received 5 June 1981; accepted for publication 29 July 1981 Soft X-ray appearance potential spectroscopy (SXAPS) and inverse photoemission (IPE) have been employed to study the oxidation of a polycrystalline nickel sample. Both methods probe empty electronic states. The present results when supplemented by UPS data establish an experimental determination of the NiO band structure consistent with theoretical models of localized and itinerant states.
Surface Science 112 (1981) 111-132 North-Holland Publishing Company SHADOWING, FOCUSSING AND CHARGE-EXCHANGE EFFECTS THE ANGULAR DISTRIBUTIONS OF keV Ne + AND H20 + IONS S C A ' I T E R E D F R O M Cu{ 110) II. T h e
111 IN
surface geometry of the first two layers
R.P.N. BRONCKERS
and A.G.J. DE WIT
Fysisch Laboratorium der Ri)ksuniversiteit Utrecht, Princetonplein 5, 3584 CC Utrecht, The Netherlands Received 4 December 1980; accepted for publication 17 June 1981 The structure of the first and second surface layer of a Cu{ 110} crystal is investigated with low energy (keV region) Ne + and H20 + scattering. The anisotropies in the intensity of scattered Ne + ions and O - ions are measured for various elevation angles of incidence and ejection. Similarities in these anisotropies can be explained by blocking and ion-focussing effects. Differences in the anisotropies are ascribed to charge-exchange processes. The intensities of scattered ions, plotted in a so-called photogram, reflect clearly the geometry of the atoms of the first and second layer. Consequently, photograms obtained with LEIS can be used for structure analysis of single crystalline surfaces. Relative large intensities in the distributions of O - ions scattered from the Cu(1 I0) surface are explained to be caused by effects of focussing the primary ions on atoms of the .second layer by atoms of the first layer. For low primary energies (1 keV) wedge-focussing in the semi-channels was found. Similar phenomena are observed for Ne + ion scattering, but here the effects are less pronounced.