XPS study on the UV/O oxidation of H-terminated Si(110) surface

Nakano, Takuya*; Togashi, Hideaki*; Matsumoto, Mitsutaka*; Yamamoto, Yoshihisa*; Suzuki, Yasushi*; Teraoka, Yuden; Yoshigoe, Akitaka ; Suemitsu, Maki*

Time evolution of oxide layers in the H-terminated Si(110) surface by the UV/O treatment at room temperature was observed by photoemission spectroscopy with synchrotron radiation. Special oxidation mechanisms for the H-terminated Si(110) surface were found. Si(110) surfaces were hydrogenated by HF treatments. The surface was irradiated and oxidized by UV light (253.7, 184.9 nm) of a low pressure Hg lamp in the air. The UV/O irradiation time dependence of oxide thickness showed a step-wise profile. The step width was about 0.2 nm. The value is close to one oxide layer thickness (0.19 nm) for the Si(110) surface. Si atoms at the Si(110) surface are categolized to A bonds which are chain-like dense bonds, and B bonds which connect up and down A bond chains. The step-wise oxidation behaviour is reasonable if oxidation at the B bonds, in which oxidation strain is smaller than that of A bonds, has larger reaction rate than at the A bonds.