XPS study of the growth kinetics of thin films obtained by thermal oxidation of germanium substrates

X-ray photoelectron spectroscopy (XPS) has been used to investigate the oxi dation of (011) and (001)Ge surfaces. The sample surfaces were CP4 etched t hen pre-annealed under vacuum at T=600 degrees C or Ar-sputtered before the oxidation. The oxidation treatments have been carried under pure dry oxyge n atmosphere and for different durations. The results show that, at the ear ly stages of the oxidation process, the oxide layer contains different oxid ation states of germanium. As the oxidation duration increases, the proport ions of the high oxidation states (Ge4+ and Ge3+) increase at the expense o f those of Ge1+ and Ge2+ following first-order kinetics. Very small values of the oxide thickness that were calculated suggest the formation of island s of germanium oxide that cover part of the surface. The argon sputtering p rior to the oxidation treatment enhances the growth rate of the oxide film during the first stage of the oxidation process. (C) 1999 Elsevier Science BN. All rights reserved.