Lateral surface diffusion at Si/SiO2 interfaces was observed at nanometer scale using photo-electron emission microscopy combined with synchrotron soft X-ray excitation. The samples investigated were Si/SiOx micro-patterns prepared by O2+ ion implantation into Si (001) wafer using a mask. The lateral spatial resolution of the photo-electron emission microscopy system was about 41nm. The brightness of each spot in the photo-electron emission microscopic images changed depending upon the photon energy around the Si K-edge, in proportion to the X-ray absorption intensity of the corresponding valence states. It was found that the lateral diffusion occurred at a 400 to 450C lower temperature than that reported for the longitudinal diffusion at the Si/SiO2 interface. It was also found that no intermediate valence states such as SiO (Si2+) existed at the Si/SiO2 interface during diffusion. The observed differences between lateral and longitudinal diffusion were interpreted by the sublimated property of SiO.

Microscopic Observation of Lateral Diffusion at Si-SiO2 Interface by Photoelectron Emission Microscopy using Synchrotron Radiation. N.Hirao, Y.Baba, T.Sekiguchi, I.Shimoyama, M.Honda: Applied Surface Science, 2011, 258[3], 987-90