Specular reflection of fast ions at a single crystal surface

Abstract

The interaction of fast ions with a solid surface is studied by the specular reflection of MeV H + and He + ions from clean (001) surfaces of SnTe single crystals. Oscillatory structure is observed in the energy spectra of the reflected He ions. This indicates that a part of the incident ions penetrate inside the crystal and travel for a few wavelengths of oscillatory motion in the (001) planar channel before reappearing at the surface. The position dependent stopping power is obtained to be proportional to E − 1 2 exp(−0.15x/a TF ) , where x is the distance from the surface. A large difference is observed in the charge state distribution between the specular reflection and the transmission through a self-supporting foil. This is attributed to the fact that the specularly reflected ions interact exclusively with the valence electrons. It is found that the velocity of convoy electrons emitted at the glancing-angle incidence of He ions is faster than that of the incident ions. This may be due to the acceleration of convoy electrons by the dynamical image potential induced by ions near the surface.