STRUCTURAL-ANALYSIS OF THE INITIAL INTERACTION BETWEEN OXYGEN AND A CLEAN SI(100) BY TIME-OF-FLIGHT AND RECOILING SPECTROSCOPY

The structure of both Si(100) in situ thermally annealed Si(100) at 13 73 K and Si(100) exposed to dry oxygen at room temperature in the rang e 5 to 1700 Langmuirs, have been studied using time of flight and reco iling spectroscopy (TOF-SARS). Structural analyses were performed by r ecording the intensities of recoiled oxygen and silicon ions as a func tion of azimuthal angle. The results show that (1) the clean annealed Si(001) is dimerized, (2) oxygen chemisorbs at the surface at the Si-u nsaturated bond, which are left unoccupied after the (2 x 1) reconstru ction, and (3) at 100 L and above the Si surface is reconstructed into a (Ix 1) structure with the oxygen binding to the broken Si-Si dimer bonds.