STM STUDY OF LOW-PRESSURE ADSORPTION OF SILANE ON SI(111)7X7

We report a study of silane adsorption on the Si(111)7 x 7 surface. We have been interested in the first stages of chemisorption at room tem perature. Reactive sites of the unit cell have been clearly identified on Scanning Tunneling Microscopy (STM) images: the reaction involves the rest atom and the adjacent adatom of the DAS structure with prefer ential adsorption on the center adatom. We propose an original chemiso rption mechanism which leads to the formation of two SiH2 species by c hemisorption and involves the breaking of Si-Si backbonds of the adato m.