Laser-induced bond breaking and structural changes on Si 111/-7=7 surfaces

We review the structural changes on the Si 111.-7=7 surface induced by irradiation of laser pulses with fluences below thresholds of melting and ablation. Atomic imaging of the irradiated surface by scanning tunnelling microscopy has shown that the bond breaking of adatoms of this 7=7 structure, associated with Si-atom desorption, is induced by an electronic process. Bond breaking efficiency is strongly site-sensitive, resonantly wavelength-dependent, and highly non-linear with respect to the excitation intensity. The electronic process responsible for bond breaking is shown to originate from non-linear localization of excited species generated from surface electronic states. q1998 Elsevier Science B.V.