Anisotropy effects in physical sputtering investigated by laser-induced fluorescence spectroscopy

We report in this article on experimental investigations of angle and energy dependencies of energy spectra of sputtered metal atoms and on deviations from linear cascade theory (Sigmund-Thompson model). Tungsten and titanium targets are bombarded by noble gas ions in the energy range between 0.2-5 keV. Energy distributions have been determined by laser-induced fluorescence spectroscopy with scanning of narrow bandwidth dye laser radiation over the Doppler broadened absorption. The geometry adopted makes it possible to vary both the angle of observation of the sputtered particles and the angle of incidence of the projectiles independently of each other. The observed differences to the theory mentioned are compared both with analytical models and with TRIM.SP-Monte Carlo simulations. The influence of direct recoil atoms on the energy spectrum is discussed in particular.