Laser ablation of ZnSe using pulsed 193-nm irradiation

Plasma jets have been produced by the pulsed laser ablation of bulk ZnSe targets. Electrical measurements show that a sudden increase in ion yield occurs at a threshold pulse energy density of 210 mJ cm−2 pulse−1. The plasmas obtained do not exhibit overall electrical neutrality, but have a net positive charge, while the ZnSe target develops a corresponding negative charge. The initial ion translational kinetic energies are also found to be very low, <1 eV. These observations suggest that the ablation process is the result of a buildup of photogenerated holes at the semiconductor surface sufficient to result in disintegration of the lattice and rapid vaporization at low thermal energies.