CALCULATION OF THE ELECTRONIC-STRUCTURE AND THE LINEAR OPTICAL-RESPONSE OF THE SB- AND SN-SI(111)ROOT-3X-ROOT-3 SURFACES

A self-consistent tight-binding technique has been employed to calcula te the electronic structures of the Sb- and Sn-Si(111)root 3 x root 3 surfaces. For the Sn reconstructed surface, two filled and one unfille d surface states as well as one straddling the Fermi level were calcul ated. Three filled and two unfilled surface states were calculated for the Sb reconstructed surface. These surface state positions are in go od agreement with experiments. We have also calculated the imaginary p art of the surface dielectric function, epsilon(2), the surface dielec tric function anisotropy and the corresponding reflectance anisotropy spectra for these reconstructed surfaces. For comparison we have also calculated the difference between the imaginary parts of the surface d ielectric functions for the Sn-Si(111)root 3 x root 3 and Si(111)root 3 x root 3 surfaces.