Effects of annealing on the lattice parameter of polycrystalline CdS thin films

Cubic CdS (beta-CdS) polycrystalline thin films were prepared on glass substrates by chemical synthesis at 80 degreesC. Samples were subjected to thermal treatments (TT) in the range of temperatures (T) 180 - 500 degreesC during 30 hours in different ambients. Annealing in air and in H-2 produces in US larger lattice parameter enlargements (less than or equal to 2.5 %) when T of TT increases up to T less than or equal to 500 degreesC. Whereas, annealing in Ar + S-2 and vacuum provokes intermediate (less than or equal to 1.2 %) and smaller (less than or equal to 0.9 %) maxima values of the lattice parameter increments, respectively. Energy band gap (E-g) as a function of T of TT and as a function of the lattice parameter has been also studied where it was observed that E-g behaves in very different manners depending on the ambient chosen for annealing.