Change in the density of states of valence electrons in semiconductors implanted with low-energy ions

Aim here was to determine the influence of the disorder at the Si (111) single-crystal surface resulting from Ba ion implantation on the density of states of the valence electrons. The measurements were carried out in ultra high vacuum equipment with a four-grid quasi-spherical analyzer, which enabled to perform the investigations using electron spectroscopy and low-energy electron diffraction (LEED) methods. The beam of primary electrons with an energy spread of less than 0.5 eV was directed perpendicular to the (111) edge of a silicon single crystal mounted at the center of curvature of the analyzer. Thermal treatment of the surface and ion bombardment were carried out in different chambers.