A search for subsurface dopants on hydrogen-terminated Si(111) surfaces

Dopant atoms located beneath the hydrogen terminated Si(111) 1 x 1 surface have been observed by scanning tunneling microscopy (STM) and barrier-height (BH) imaging. Since the hydrogen terminated Si(111)1 x 1 surface has no significant surface states within the band gap, the screening effect of this surface on subsurface dopants is expected to be weak, compared to that on clean silicon surfaces. this enables us to observe electrically charged dopants located near the surface by STM. Simultaneously obtained BH images show a local reduction of,surface potential above the dopant sites. The average reduction of the tunneling barrier height is similar to1.5 eV.