NEGATIVE-ION FORMATION FROM SICL4 ADSORBED ON SI(100)

Electron stimulated desorption of negative ions has been investigated with SiCl4 adsorbed at Si(100). Cl- ion is the only negatively charged species detected and the ion yield peaks at 1 ML coverage when SiCl4 is adsorbed at a clean Si(100) surface. The higher ion yield from the first monolayer of SiCl4 is interpreted as due to charge transfer from the surface to the lowest unoccupied level of SiCl4, in association w ith an enhanced symmetry change from T-d to C-3v.