CHARGE-STATE DISTRIBUTION OF MEV HE IONS SCATTERED FROM THE TOPMOST ATOMIC LAYER OF THE SNTE(001) SURFACE

The charge-state distribution of 0.5-MeV He ions scattered from a SnTe(001) surface has been investigated using a new technique of high-resolution high-energy ion scattering spectroscopy. The ions scattered from successive atomic layers can be resolved in the energy spectra of the scattered ions. The observed charge-state distribution of the ions scattered from the topmost atomic layer coincides with that of ions scattered from the subsurface region and does not depend on the incident charge state but depends on the exit angle. The observed exit-angle dependence is explained by a model which includes thc charge-exchange process with the valence electrons in the tail of the electron distribution at the surface.