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Ultraviolet photoemission studies of chemisorption and point defect formation on ZnO nonpolar surfaces
A334 InAs only two clearly distinct groups of levels can be identified. The upper one always corresponds to centers with one dangling bond on a metallic atom, while the lower one contains the levels associated to all the other possibilities we have investigated. For InP, levels associated with two dangling bonds on a metallic atom are raised from the lower group. This is in agreement with the other available theoretical results. A discussion of the experimental data in the light of our results is presented.
Surface Science 99 (1980) 1 3 8 - 1 5 8 © North-Holland Publishing Company ULTRAVIOLET PHOTOEMISSION STUDIES OF CHEMISORPTION AND POINT DEFECT FORMATION ON ZnO NONPOLAR SURFACES W. G O P E L *, R.S. B A U E R a n d G. H A N S S O N
Xerox Pale Alto Research Center, Pale Alto, California 94304, USA Received 25 September 1979; accepted for publication 13 December 1979 Ultraviolet photoemission (He I and He II) studies are reported on point defect formation as well as CO2 and 02 interaction with ZnO(1010) under thermodynamically well defined conditions. Physisorption spectra can be correlated with UPS spectra in the gas phase if a uniform relaxation/polarization shift is taken into account. CO2 chemisorption may be characterized by formation of carbonate like surface complexes. Small concentrations of intrinsic point defects lead to significant changes in the surface electronic structure and provide specific CO2 chemisorption sites which are intermediates during heterogenous oxidation of CO on ZnO.
Surface Science 99 (1980) 157-164 © North-Holland Publishing Company ELECTRONIC AND STRUCTURAL PROPERTIES OF STEPS ON CLEAVED SEMICONDUCTOR SURFACES S. K R U E G E R a n d W. M O N C H
Laboratorium fiir Festk6rperphysik der Universitdt Duisburg, D-4100 Duisburg, Germany Received 26 November 1979; accepted for publication 2 Feburary 1980
The work function of clean, cleaved p-Si(111) surfaces was measured in dependence of the density of cleavage steps. The contact potential difference CPD was observed first to increase then to decrease linearly with increasing step density. This dependence is caused by an increase in band bending, which saturates at a density of approximately l X 106 steps per era, and a decrease of the surface dipole which is proportional to the density of steps. Since the 2 × 1 reconstruction of the cleaved Si surface is ionic and buckled it increases the surface dipole moment compared with the 1 × 1 structure. Thus, a decrease of the surface dipole may be caused by removal of the 2 × 1 reconstruction on part of the step terraces. The experimental data give a width of about 28 A for the unreconstructed stripe along the step edge.
Surface Science 99 (1980) 1 3 8 - 1 5 8 © North-Holland Publishing Company ULTRAVIOLET PHOTOEMISSION STUDIES OF CHEMISORPTION AND POINT DEFECT FORMATION ON ZnO NONPOLAR SURFACES W. G O P E L *, R.S. B A U E R a n d G. H A N S S O N
Xerox Pale Alto Research Center, Pale Alto, California 94304, USA Received 25 September 1979; accepted for publication 13 December 1979 Ultraviolet photoemission (He I and He II) studies are reported on point defect formation as well as CO2 and 02 interaction with ZnO(1010) under thermodynamically well defined conditions. Physisorption spectra can be correlated with UPS spectra in the gas phase if a uniform relaxation/polarization shift is taken into account. CO2 chemisorption may be characterized by formation of carbonate like surface complexes. Small concentrations of intrinsic point defects lead to significant changes in the surface electronic structure and provide specific CO2 chemisorption sites which are intermediates during heterogenous oxidation of CO on ZnO.
Surface Science 99 (1980) 157-164 © North-Holland Publishing Company ELECTRONIC AND STRUCTURAL PROPERTIES OF STEPS ON CLEAVED SEMICONDUCTOR SURFACES S. K R U E G E R a n d W. M O N C H
Laboratorium fiir Festk6rperphysik der Universitdt Duisburg, D-4100 Duisburg, Germany Received 26 November 1979; accepted for publication 2 Feburary 1980
The work function of clean, cleaved p-Si(111) surfaces was measured in dependence of the density of cleavage steps. The contact potential difference CPD was observed first to increase then to decrease linearly with increasing step density. This dependence is caused by an increase in band bending, which saturates at a density of approximately l X 106 steps per era, and a decrease of the surface dipole which is proportional to the density of steps. Since the 2 × 1 reconstruction of the cleaved Si surface is ionic and buckled it increases the surface dipole moment compared with the 1 × 1 structure. Thus, a decrease of the surface dipole may be caused by removal of the 2 × 1 reconstruction on part of the step terraces. The experimental data give a width of about 28 A for the unreconstructed stripe along the step edge.