LASER-INDUCED ELECTRONIC-BOND BREAKING AND DESORPTION OF ADATOMS ON SI(111)-(7X7)

Laser-induced structural changes on the Si(111)-(7 x 7) surface were s tudied for laser fluences below thresholds of melting and ablation. Th e adatoms of the reconstructed structure are removed selectively by an electronic process, and Si atoms in the electronic ground state are e jected with a peak translational energy of 0.15 eV. The electronic pro cess of this bond breaking of adatoms exhibits the site-sensitive effi ciency which shows a resonant wavelength dependence and is highly supe rlinear with respect to the excitation intensity.