TOPICAL REVIEW: Treatment of semiconductor surfaces by laser-induced electronic excitation

We review how semiconductor surfaces can be modified by laser irradiation. We deal solely with phenomena induced by electronic excitation, and compare the processes induced by laser irradiation with those induced by electrons from scanning tunnelling microscope tips. The ejection of host atoms from perfect surface sites, or of hydrogen from hydrogen-terminated surfaces, takes place either by single excitation for high-energy photons or with multiple excitation for low-energy photons, even though the quantum yield for ejection by single excitation is extremely low. The atoms neighbouring defects on surfaces are ejected with higher probabilities than those on perfect sites. There appear to be anti-bonding states, embedded in the continuum, such that excitation to them can induce atomic ejection. When the photon energy is too small, multiple photoexcitation or dense excitation is needed to reach these anti-bonding states. Possible applications of laser surface treatments are discussed.