Angular distributions of sputtered particles

Abstract

The trajectories of neutral particles ejected from surfaces bombarded by keV projectiles have been precisely determined. The neutrals are detected with high efficiency by selective postionization of the desorbed atoms by laser initiated multiphoton resonance excitation. By employing a pulsed beam of primary Ar+ ions, the velocity of the desorbed atoms may be selected by appropriate timing between this pulse and the pulse of ionizing laser radiation. These ions are then imaged to a position-sensitive detector for angle determination. Under present conditions we can detect neutrals whose kinetic energies vary from 0.2–50 eV into a total enclosed angle of over 100° using a total dose of <1012 incident Ar+ ions/cm2. Results are illustrated for polycrystalline Rh, Rh{111}, and Rh{111} covered with adsorbed oxygen. The measurements also illustrate a number of difficiencies of theoretical treatments of the particle/solid interaction problem.