Optical properties of CdI2 thin films

The transmittance (T) of thin films of CdI2: prepared by thermal evaporatio n technique on quartz substrates, have been measured over the wavelength ra nge 200-900 nm. From analysis of the transmittance data, the optical consta nts, the refractive index (n) and the extinction coefficient (k), have been studied. Analysis of the refractive index (n) yields a low frequency diele ctric constant, average oscillator strength and average oscillator energy. From analysis of the absorption coefficient (alpha), the fundamental absorp tion edge can be determined. Both allowed direct transitions and allowed in direct transitions are observed. The composition of films is checked using energy dispersive X-ray (EDX) spectroscopy technique. X-ray diffraction (XR D) measurements showed that the CdI2 films evaporated at room temperature s ubstrates were characterized by a polycrystalline form. At large thicknesse s the films indicated the inhomogeneity. The effect of annealing temperatur e (up to 523 K) on the film properties has been studied.