1. Mäder¹, A. Zehe², A. Ramírez³, ¹Technische Universitaet Dresden, Germany, ^2,3Universidad Autónoma de Puebla, ²FCFM, ³ICUAP, 72550, Puebla, México.

Surface reconstruction of {111}- and {100}- oriented silicon is studied. Decontamination by ex situ chemical processes and in situ thermal treatment is a key requirement for a controlled reconstruction to be observed. Only after a high temperature annealing at 1200 ºC for several minutes was the (7x7) and (2x1) reconstruction obtained, which we explain by SiC desorption. Once generated the reconstruction maintains stable for a long time even at increased gas pressure in the UHV-chamber.