FAST ANNEALING OF II-VI COMPOUNDS BY PULSED-LASER IRRADIATION

The effects of pulsed laser annealing of CdTe (containing small quanti ties of Zn or Hg) are described for single crystals and thin film samp les. The influence of laser power, wavelength, number of applied pulse s, and homogenization on the morphological changes and some physical p arameters are investigated with the help of scanning electron microsco py (SEM), x-ray diffraction (XRD), UV/VIS absorption spectrophotometry and (photo)electrochemical characterization. Melting of the sample su rface was observed in most cases at the laser pulse energies used; the surface modifications as seen by SEM depended in a characteristic way on laser wavelength and photon density. Use of homogenized beams led to a restructuring of the surface, entailing in-depth melting with the formation of holes and spongy structures, in particular upon multi-pu lse irradiation at lambda = 532 nm. In general, surface melting promot ed the healing of cracks which were sometimes formed by laser-induced thermal shock in the crystal plates (such cracks were not found in the thin films). Surface melting and material loss by evaporation is acco mpanied by some amorphization and maybe caused by a change in doping p rofile and/or stoichiometry near the surface.