PHOTOELLIPSOMETRIC STUDIES ON CDTE THIN-FILMS

Photoellipsometry has been used to study the optical properties of CdT e thin films prepared by electrodeposition, physical vapor deposition (PVD) and close spaced vapor transport (CSVT) under different depositi on conditions. Pseudodielectric functions (both real and imaginary) ha ve been calculated for samples with and without the pumping beam on. A n anomalous peak is observed in the pseudodielectric function spectra of CdTe samples prepared by electrodeposition and CSVT methods. This p eak does not appear in CSVT samples prepared under high vacuum (simila r to 10(-6) mbar) or in samples prepared by PVD. The dependence of thi s peak on pump intensity, pump beam energy and deposition conditions h as been observed. The peak is found to disappear below a threshold int ensity (similar to 1 mW/cm(2)) of pump beam. A plausible reason for th e above observations is the presence of oxygen in the electrodeposited samples and in CSVT samples prepared in a low vacuum environment.