Structural and optical properties of chemically deposited Cd(S-Se): CdCl2, Sm films

Results of SEM and XRD studies, optical absorption and photoluminescence (PL) emission spectra and photoconductivity (PC), rise and decay studies are reported for Cd(S-Se): CdCl2, Sm films prepared by chemical deposition method on glass substrates at 60°C in a water bath. SEM studies show ball-type structures along with voids which are related to layered growth. XRD studies show prominent diffraction lines of CdS and CdSe along with some peaks of CdCl2 and impurity Sm. The values of strain (ɛ), grain size (D) and dislocation density (δ) are evaluated from XRD studies and the nature of crystallinity of the films are discussed. Optical absorption spectra also show the presence of Sm in the lattice. From the results of optical absorption spectra, the band gaps are determined. PL emission spectra of Cd(S-Se) consist of two peaks which are related to the edge emission of CdS and CdSe involving excitons. In Sm-doped emissions corresponding to transitions 4G5/2 to 6H5/2, 6H7/2 and 6H9/2 are observed. Sufficiently high photo current (Ipc) to dark current (Idc) ratios with a maximum value of the order of 106 are also obtained in some special cases. This high photosensitization is related to increase in mobility and life time of carriers due to photo excitation.