Control of the surface chemistry to prepare a robust termination on the Ge surface is crucial for the development of high-end Ge devices. In this study, oxidation of a H-terminated Ge surface was studied in air ambient and H2O using a multiple internal reflection Fourier transform infrared spectroscopy (MIR FT-IR) technique. Ge surface treated in less diluted HF exhibited a stronger Ge-H peak intensity, and the surface was easily oxidized in the air ambient. Therefore, it is believed that the treatment of the Ge surface in highly diluted HF solution has an advantage in suppressing the oxidation of Ge in the air ambient. For the oxidation of Ge(1 0 0) surface in air ambient, the Ge surface is attacked by oxidizing agents to break Ge-H and Ge-Ge bonds, and the transition GeOx layer is first formed, followed by a layer-by-layer GeO2 formation with the increase in exposure time. When the H-terminated Ge surface was treated in H2O, GeOx was mainly formed, the thickness of the oxide layer was not changed with an increase in treatment time, and the Ge surface was maintained in a suboxide state, which exhibits a different oxidation mechanism from that in air ambient. (C) 2008 Elsevier B.V. All rights reserved.