Photoemission study of the oxidation and the post-annealing behaviors of a Pr-covered Si(1 0 0) surface

Electron spectroscopy has been used to investigate the oxidation and the post-annealing behaviors of a Pr/Si surface. The Pr overlayer with a thickness of about 20 A ° was deposited on Si(1 0 0) at room temperature. It was found that some of the Pr atoms form chemical bonds with Si. An initial fast oxygen adsorption on the Pr/Si surface is mainly associated with the formation of Pr2O3. The presence of praseodymium enhances the oxidation rate of the substrate. The silicon atoms diffuse from the Pr–Si bonds as well as the substrate into the Pr2O3 layer, forming a Pr–O–Si silicate. SiO2 was also observed during oxygen adsorption, which was caused by the oxidation of the Pr–O–Si silicate in the vicinity of the top surface. At high oxygen exposures, a slow further oxygen uptake is related to the growth of the Pr–O–Si bond and SiO2. Both Pr2O3 and SiO2 decrease in intensity while the Pr silicate grows with annealing temperature. # 2003 Elsevier B.V. All rights reserved