LASER-INDUCED BOND BREAKING OF THE ADATOMS OF THE SI(111)-7X7 SURFACE

Tunneling images of the Si(111)-7 x 7 surface before and after laser i rradiation have been compared. Examination of more than 300 unit cells shows that the number of unit cells with missing center adatoms incre ases by 2.48 eV laser pulse irradiation at fluences slightly above the threshold laser fluence above which the emissions can be detected. No indication of melting is observed in the unit cells with missing adat oms. The results give clear evidence that laser-induced atomic emissio ns from semiconductor surfaces are electronic and site selective.