DETERMINATION OF THE COMPLEX DIELECTRIC FUNCTION OF CDTE(110)1X1 SURFACE BY POLARIZED SURFACE DIFFERENTIAL REFLECTIVITY

We present a determination of the complex surface dielectric function (SDF) of the CdTe(110)1 x 1 surface obtained by using polarized surfac e differential reflectivity data (Delta R/R) obtained for the light el ectric vector along the [1 $($) over bar$$ 10] and [001] directions, i .e. ''parallel'' and ''perpendicular'' to the natural chains of the un reconstructed (110) surface. In the energy range below 3.3 eV the imag inary part of the SDF (epsilon'') and Delta R/R are very similar while above 3.3 eV they differ markedly because of the effect of bulk contr ibution. Three mainly isotropic structures are clearly visible in the epsilon'' spectra at the following photon energies: 2.7, 3.3 and 3.65 eV. The interpretation of such structures in terms of optical transiti ons between surface state bands as derived from direct and inverse pho toemission is shown. Moreover, the effective number of electrons per a tom participating in the optical transitions is calculated for energie s up to 4.0 eV.