The depth profiles of so-called sub-oxides in the surface region, of 100nm-thick films which had been annealed in vacuum at 800C, were measured by using angle-resolved X-ray photo-electron spectroscopy. It was found that the amount of sub-oxide which was distributed beneath the surface increased rapidly, and almost saturated, with annealing time. The change in the amount of sub-oxide which was present on the surface was very small and increased gradually with annealing time. This indicated that very fast out-diffusion of SiO molecules through thick SiO2 films took place at temperatures which were as low as 800C, and led to desorption from the surface.

Y.Takakuwa, M.Nihei, N.Miyamoto: Japanese Journal of Applied Physics - 2, 1993, 32[4A], L480-3