Wide range temperature dependence of reflection high-energy electron diffraction rocking curve from a Si(111)7x7 surface

In order to determine the Debye parameter for the surface layer of Si cryst al, we have measured the rocking curves of reflection high-energy electron diffraction (RHEED) from a Si(111)-7x7 surface at temperatures extending ov er a wide range, 293-1073 K. From the analysis of the dynamical calculation of RHEED intensity taking account of the thermal diffuse scattering, the a datoms and rest atoms largely shifted upward compared with the atomic posit ions derived by Brommer et al. using ab initio molecular-dynamics scheme [P hys. Rev. Lett. 68, 1355 (1992)] and the optimum Debye temperature has been estimated at 420 K, which is much lower than that of bulk Si (505-658 K). Since the Debye temperature is considered to be an averaged value in a few surface layers, the difference means that the vibrational amplitude of surf ace atom is large compared to bulk atom. (C) 2000 American Vacuum Society. [S0734-2101(00)02303-4].