Laser-induced electronic desorption from InP surfaces studied by femtosecond nonresonant ionization spectroscopy

Laser-induced desorption from clean surfaces of InP(110)-(1x1) and InP(100)-(4x2) has been studied for laser fluences well below melt and ablation thresholds. For detecting desorbed neutral species simultaneously with hi,oh sensitivity, we used femtosecond nonresonant ionization spectroscopy with a detection limit as low as the order of 10(-7) monolayers per pulse. Species desorbed are P, P-2, and In, the relative yields of which are strongly dependent on the surface structures, and the efficiencies of desorption for the three species are superlinear with respect to the excitation intensity. Desorption yields of all species decrease with increasing number of laser shots on the same spot, suggesting desorption from preexisting surface defect sites. Time-of-flight measurements for P, P-2, and In from InP surfaces revealed that the peak flight time and the velocity distribution did not depend on the excitation intensities. The mechanism of the laser-induced desorption is discussed based on these results.