Laser-Induced Sputtering from CdS and GaAs

The laser-induced sputtering from semiconductors not only involves basic problems about lattice dynamics and chemical reactions in dense electron-hole (e-h) plasmas, but also gives important clues to wide applications in the laser-controlled bulk and surface processes. Time of flight (TOF) spectra of emitted particles have been used as a measure of the surface temperature during the laser annealing of Si by fitting a Maxwellian distribution function (1). For the compound semiconductors, however, TOF spectra of the neutral particles showed a velocity distribution apparently deviated from the Maxwellian one(2). Three possible mechanisms have appeared for the dynamics of atoms in pulsed laser-irradiated semiconductors. Those are (1) vaporization of molten phase(1), (2) instability of e-h plasma and concomitant phase transition(3), and (3) non-radiative relaxation as a result of two hole localization in e-h plasma(2). While these are rather concerned with the neutral particle ejection, knowledge about the relation of ions and neutrals is still scarce. CdS and GaAs are very interesting semiconductors from the view-point of practical use and basic problems of optical properties. We will employ here a dynamic mass spectroscopic method with a pulsed laser and discuss the emission of ions and neutrals.