OPTICAL ANISOTROPY OF GE(001)

The surface induced optical anisotropy in the electronic structure of clean Ge(001)2 x 1 was studied with an ellipsometer at normal incidenc e. The change in the reflection difference between light polarized par allel and perpendicular to the dimer bond at this surface upon either adsorption of molecular oxygen or Ar+ ion bombardment was recorded. Bo th procedures were found to give the same results. It was possible to obtain a qualitative agreement of the optical spectrum recorded and th e position and parity of the occupied and unoccupied surface states kn own on the clean surface.