SYMMETRY OF, AND POLARIZED-LASER-INDUCED REACTIONS ON, SI(111) CL2 SURFACES STUDIED BY 2ND-HARMONIC GENERATION

The surface symmetry of, and the polarized-laser-induced reactions on, Si (111)/Cl-2 surfaces have been studied using second-harmonic genera tion (SHG). The outermost surface originated SHG signals, generated by 1.1, 1.3 and 2.0 eV probe., show the modified 3 m symmetries enhanced along the [<2(11)over bar>] direction, probably because of a macrosco pic asymmetric surface structure along the [<2(11)over bar>] orientati on. On the other hand, the SHG signals originated by the direct bulk t ransition, generated by 1.6 and 1.7 eV probe, show good 3 m symmetries rather reflecting the symmetry of bulk Si. The threshold power densit ies of the laser-induced Si (111)/Cl reaction showed significant depen dence on the pump polarization with respect to the crystal orientation of the sample surface, and no important dependence on that with respe ct to the plane of incidence. (C) 1998 American Vacuum Society. [S0734 -2101(98)00805-7].