Abstract
The emission of gas phase particles from a GaAs surface, due to irradiation at 1064 nm by an unfocussed Q-switched Nd:YAG laser beam, has been studied. Mass spectra have been recorded with the aid of a quadrupole mass spectrometer, and the ion-neutral ratio of the emitted particles has been measured with an electrical diode set up. The applied incident laser radiation power density was varied in the range 1.2–9.6 × 107 Watts/cm2 and was delivered as 10 ns (fwhm) long pulses. It appeared that mainly Ga atoms and As2 molecules were emitted, together with minor amounts (<1%) of Ga2 and GaAs molecules. Besides the emission of neutral particles, the formation of Ga+ atomic ions was observed. By measuring the ratio of Ga+ ions and Ga neutral atoms it could be shown that the (ionic) particle emission is governed by a thermal mechanism for 1064 nm incident radiation. This latter experimental result differs from that obtained if a ruby laser (694 nm) is used as the radiation source.