Photoconductivity and photoluminescence in chemically deposited films of CdSSe:CdCl2,Ho

Abstract

Results of the scanning electron microscopy (SEM), X-ray diffraction (XRD), optical absorption, photoconductivity (PC), and photoluminescence (PL) studies for the CdSSe:CdCl2,Ho films are presented in this paper. The SEM studies of different CdSSe films show a layered growth structure. A crystalline nature of the films is observed in the XRD studies. The regions with stacking fault were also observed in the X-ray diffractograms. The optical absorption spectra of these films show variations corresponding to the band gaps and the grain-sizes obtained under various deposition conditions and also with annealing. The effect of flux, impurities and annealing on the saturated photo to dark current ratio Ipc/Idc is observed in the PC rise and decay studies. The maximum value of Ipc/Idc ∼107 is obtained for the impurity doped annealed films. The PL emission spectra of CdSSe films show two emission peaks associated with the annihilation of free excitons and the transitions between shallow donor and deep acceptor states. In CdSSe:CdCl2,Ho films, two PL emission peaks are observed at 495 nm and 545 nm corresponding to the transitions 5S2→5I8 and 5F3→5I8, respectively, in Ho. The effect of pH on PL and grain size is also included in the present studies.

Morphology and band gap controlled AACVD of CdSe and CdS Se1− thin films using novel single source precursors: Bis(diethyldithio/diselenocarbamato)cadmium(II)

“…Raman spectra showed peaks at $195 and $ 400 cm À 1 which were shifted from the actual CdSe Raman LO and overtones at 212 and 410 cm À 1 as reported previously [48,49] (Fig. 7(a)).…”

“…Raman spectra of CdSe thin films at 7 and 14 mmol precursor concentration with an excitation wavelength of 514.5 nm showed a strong peak at 210 cm À 1 which is attributed to the optical phonon at 210 cm À 1 (LO) and an overtone at 420 cm À 1 (2LO) as reported previously [48,49] (Fig. 4(a)).…”

“…CdS 0.5 Se 0.5 films obtained by electrochemical deposition on indium tin oxide (ITO) showed highest photoelectrochemical conversion efficiency [47]. Bhushan et al reported the PC growth and decay, and PL emission spectral studies of chemically deposited films of CdSSe with the effect of variations in the composition, doping of flux and impurity and annealing on the films [48].…”

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

“…Higher volumes of sodium seleno sulphate (Na 2 SeSO 3 ) were added for increasing the concentration of CdSe. Thus, the formation of more sulphur could be expected, enhancing the emission in its presence (Bhushan and Oudhia 2008). A prominent peak at 505 nm in Cd-rich single crystals of CdS at room temperature was also reported earlier (Kokubun and Kaeriyama 1975).…”

“…Owing to similar excitonic nature in both CdS and CdSe, this emission can be attributed to the radiative decay of the free exciton. The peak at 494 nm may be attributed to the exciton bound to neutral donor levels formed by sulphur/excess Cd (Bhushan and Oudhia 2008). Higher volumes of sodium seleno sulphate (Na 2 SeSO 3 ) were added for increasing the concentration of CdSe.…”