Low-energy-electron loss spectroscopy of ZnTe (110) and (111) surfaces. II. Oxidation properties

The oxidation properties of ZnTe (110) and (111) surfaces have been studied by low-energy-electron loss spectroscopy and Auger-electron spectroscopy. Oxygen adsorption of about half-monolayer coverage was observed at an exposure of ${10}^{13}$ L of molecular oxygen, for both ordered (110) and (111) surfaces. Electronbeam irradiation drastically stimulated oxidation and oxygen adsorption larger than one-monolayer coverage occurred. Loss spectra of the oxygen-contamined surfaces exhibit an oxygen-derived surface state lying ∼ 0.3 eV above the valence-band maximum, probably within the band-gap region, for the surface with adsorbed oxygen, and a Zn-$3d$ core-level loss due to ZnO and a Te-$4d$ core-level loss due to Te${\mathrm{O}}_2$ for the heavily oxidized surface. This finding implies that both zinc and tellurium oxides are involved in the oxidation of ZnTe. The chemical compositions of the clean and oxidized surfaces are discussed by using a layer model.