Bond scission induced by electronic excitation in solids: A tool for nanomanipulation

A review is given on the atomic processes induced by electronic excitation of nonmetallic solids, including defect formation, transformation of defect structures, atomic emission from surfaces and surface modifications. It is pointed out that the processes involve bond scission. Two major issues, the localization of the electronic excitation energy and the energetics, are discussed. It is emphasized that the major features of the processes are different, depending on the presence and absence of self-trapping of excitons and on the bond strength with respect to the band-gap energy. Bond scission can be induced at any sites in solids in which excitons are self-trapped, but only at defect sites in solids in which excitons are not self-trapped. The yield of the bond scission is a superlinear function of the density of excitation when the bond energy is higher than the band-gap energy. For semiconductor surfaces, on which excitons are not self-trapped and the bond strength is higher than the band-gap energy, bond scission is induced only at the sites of surface defects and its yield is a superlinear function of the density of excitation.