Low energy ion beam damage of semiconductor surfaces: a detailed study of InSb(100) using electron energy loss spectroscopy

The phonon and plasmon excitations of both n- and p-type InSb(100) have been studied using high resolution electron energy loss spectroscopy (HREELS). The effects of structural damage, induced by low energy ion bombardment, on the conduction band plasmon energy has been monitored as a function of post-bombardment annealing temperature. In all cases, the plasmon energy reaches a maximum of between 55 and 75 meV after annealing to ~ 500 K. This indicates the presence of a large excess of free-carriers in the near-surface region probably due to the presence of defect states including Sb vacancies which would act as donor states. By monitoring the plasmon energy as a function of incident electron beam energy, we exploit the potential of the HREELS technique to probe the free-carrier concentration in semiconductors over a depth range of about 200–2000 A. The degree and depth of damage induced by the sputtering process is found to be approximately 800–1000 A into the bulk of the material, corresponding to the formation of an n-type layer in this near-surface region.