EFFECT OF ADLAYER DIMER ORIENTATION ON THE OPTICAL ANISOTROPY OF SINGLE-DOMAIN SI(001)

The effect of adlayer dimer formation on the optical anisotropy of sin gle domain Si(001) is reported. Reflection anisotropy spectroscopy (RA S) from Ga and Sb adsorbed on the Si(001) surface reveals complex beha vior which depends strongly on the atomic species acid the RAS signal cannot be simply related to dimer orientation. Dimer formation in the same direction on thp surface by Si and Ga is shown to produce RAS sig nals, below the direct optical gap of Si, of the opposite sign. This c ontrasts with the simpler behavior observed for Ga and As adsorption o n GaAs(001) surfaces. (C) 1995 American Institute of Physics.