Differential reflectivity and photoemission study of ZnTe and CdTe (110) surface

The surface differential reflectivity (SDR) and photoemission methods were used to study surface electronic structure of CdTe and ZnTe (110) surface. The changes of reflectivity coefficient were caused by the changes of electric field (band bending) induced at the surface region by high power laser illumination of the sample. The SDR spectra were obtained as a function of laser power illumination. The shift of the surface potential was estimated on photoemission spectra as a shift of the Cd 4d level position caused by the laser illumination of the sample. The exponential time decay of the amplitude of SDR spectra were measured after turning of the laser illumination. The decay time constant was estimated at 22 min for clean surface of CdTe and 60 min for real surface of ZnTe. The attempts were done to discuss obtained results in the frame of the Franz-Keldysh effect description.