Microscopic observation of lateral diffusion at Si-SiO interface by photoelectron emission microscopy using synchrotron radiation

Hirao, Norie; Baba, Yuji  ; Sekiguchi, Tetsuhiro  ; Shimoyama, Iwao   ; Honda, Mitsunori*

The lateral surface diffusion at Si-SiO interface has been observed at nanometer scale using photoelectron emission microscopy (PEEM) combined with synchrotron soft X-ray excitation. The samples investigated were Si-SiO micro-patterns prepared by O ion implantation in Si(0 0 1) wafer using a mask. The lateral spacial resolution of the PEEM system was about 41 nm. The brightness of each spot in the PEEM images changed depending on the photon energy around the Si -edge, in proportion to the X-ray absorption intensity of the corresponding valence states. It was found that the lateral diffusion occurs at lower temperature than that reported for the longitudinal diffusion at the Si-SiO interface. It was also found that no intermediate valence states such as SiO (Si) exist at the Si-SiO interface during the diffusion. The observed differences between lateral and longitudinal diffusion are interpreted by the sublimated property of silicon monoxide (SiO).