Properties of r.f. sputtered cadmium telluride thin films

CdTe thin films were prepared using RF magnetron sputtering in an Ar atmosphere. Substrate temperatures in the range 100-320 C were used. XRD results showed that the films are amorphous below 200 C while above 200 C the firms were polycrystalline with cubic structure and grains preferentially oriented along the [1 1 1] crystallographic direction. SEM measurements showed significant enhancement of crystallite size with increase of T(s) or with post-preparation annealing above 400 C. The 5 K photoluminescence spectrum showed a broad (FWHM = 80 meV) band with a maximum at 1.538 eV. This band showed significant narrowing after annealing above 400 C, suggesting that it originates from transitions involving grain boundary defects. The refractive index n was determined from the interference pattern of the optical transmission. The results agree with the values of n calculated using the Jensen theory.