Clean ZnO surfaces and oxygen adsorption on the (0001) surface studied by electron spectroscopy

Abstract
The reflection electron energy-loss spectra of clean (0001), (0001) and (1100) surfaces of ZnO have been studied with primary energies in the range 60-2000 eV. The spectra are interpreted in terms of interband transitions, longitudinal bulk surface excitation modes. At low primary energies, the general shape of the spectra differs from that at higher energies and differences between the features of the polar surfaces and the neutral face are observed. Exposure to oxygen (0.08-0.13 Pa s) influences the loss spectra. Electron beam and thermal desorption effects on the loss spectra are observed and discussed in relation to physisorbed and chemisorbed states of the adsorbed oxygen. Measurements of Auger electron spectra showed a very broad oxygen KL2,3L2,3 peak, the lineshape of which is discussed in relation to the quasi-atomic model.