Distinctly different thermal decomposition pathways of ultrathin oxide layer on Ge and Si surfaces

Abstract

The thermal decomposition pathway of an ultrathin oxide layer on Ge(100) and Si(100) surfaces is examined by synchrotron radiationphotoelectron spectroscopy and ultraviolet photoelectron spectroscopy with helium Iradiation. The as-prepared oxide layer consists of a mixture of oxides, namely, suboxides and dioxides, on both the surfaces. Upon annealing, the oxide layers decompose and desorb as monoxides. However, we find that the decomposition pathways are different from each other. On annealingGe oxides, GeO 2 species transform to GeO and remain on the surface and desorb at >420 °C. In contrast, annealing of Si oxides results in the transformation of SiO to SiO 2 up to temperatures (∼780 °C) close to the desorption. At higher temperatures, SiO 2 decomposes and desorbs, implying a reverse transformation to volatile SiO species.