Origin of the peak shapes in the Auger spectrum of oxygen (KL2,3L2,3) on molybdenum

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Abstract
The Auger and ultraviolet photoelectron spectra of a molybdenum surface (temperature range: 100 degrees C-900 degrees C) with adsorbed oxygen (pressure range: 3*10-7-8*10-7 Torr) were measured simultaneously with a high-resolution Auger-photoelectron spectrometer. The oxygen KL2,3L2,3 Auger transition and the photoelectron emission from the valence state particularly, were scrutinized. Two distinct regions (I and II) of adsorption were observed as the amount of oxygen was increased. In region I where the amount of oxygen on the surface was small, the adsorbed species was atomic. However, when the amount of oxygen on molybdenum reached a particular value characterizing region II, the incorporation of oxygen began suddenly and MoO2 was formed. Accompanying this change of state of oxygen, the FWHM of the oxygen (KL2,3L2,3) Auger peak broadened from 3.75 eV to 5.75 eV.