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Singh R.S.,Government D T College Utai | Bhushan S.,Shri Shankaracharya Engineering College Bhilai | Singh A.K.,Government VYT PG College
Journal of Optoelectronics and Advanced Materials | Year: 2010

Results of SEM and XRD studies, optical absorption spectra and photoluminescence (PL) emission studies are reported for Cd(Se-S):CdCl 2,Pr films prepared by chemical deposition method on glass substrates at 60°C in a water bath (WB). SEM studies show ball type structure with voids which is related to layered growth. XRD studies show prominent diffraction lines of CdSe and CdS along with lines of CdCl2. The chemically deposited CdSe-S films are found to consist of two PL emission peaks, one at 494 nm and the other shifting from 516 nm to 577 nm with increasing concentration of Se. The peak at 494 nm may be attributed to the exciton bound to neutral donor levels formed by excess sulphur/Cd, and the other peak may be attributed to the radiative decay of the free exciton. The peak at 494 nm may also be due to the shift of bulk emission of CdS at 511 nm (nano-crystalline effect). In Pr doped films, a new intense peak appears at 598 nm (as compared to the PL spectra of base material), which may be related to the transitions in Pr-levels. Source


Singh R.S.,Government D T College | Bhushan S.,SSCET Bhilai | Singh A.K.,Government VYT PG College
Chalcogenide Letters | Year: 2010

Results of SEM, XRD, optical absorption spectra and photoluminescence (PL) emission spectra are presented for chemically deposited bulk and nano-crystalline CdSe films prepared on microscopic glass substrates. Nano-crystalline CdSe films were prepared with two concentrations of capping agents thiophenol and methanol (TPM). SEM studies show spherical shaped morphology. XRD studies show the hexagonal structure with a preferred orientation along the (002) direction of films. The average grain size decreases with increasing TPM volume. Blue shift in the absorption edge with increase in TPM volume is seen from optical absorption studies which also indicate increase in its band-gap. The grain sizes determined from such studies also lie in nano-range. The PL emission spectra show shift of peaks in the lower wavelength side due to reduction in grain size. Source


Singh R.S.,Government D T College Utai | Bhushan S.,Shri Shankaracharya Engineering College Bhilai | Singh A.K.,Government VYT PG College | Deo S.R.,Government VYT PG College
Digest Journal of Nanomaterials and Biostructures | Year: 2011

Chemical bath deposition (CBD) was used to prepare a CdSe semiconductor films on glass substrates. Scanning electron microscopic studies shows ball type structures with approximate grain size ranging between 4 nm and 8 nm with voids on uniform background. The crystallographic structure of the film and the size of the crystallites in the film were studied by X-ray diffraction. XRD measurement shows that the film is crystallized in the wurtzite phase and presents a preferential orientation along the c-axis. Optical constants such as refractive index n and extinction coefficient k, were determined from transmittance spectrum in the ultraviolet-visible (UV-VIS) regions using envelope methods. Absorption coefficient α and the thickness of the film t were calculated from interference of transmittance spectra. Optical excitation spectra showed maximum excitation at 389 nm. The photoluminescence (PL) emission spectra under this excitation consisted of two peaks at 485 nm and 531 nm wavelengths, which are attributed to the presence of one deep trapping site and electron hole recombination via trap state or imperfection site. The blue shift observed in the PL emission spectra corresponds to the nano-crystalline effect. Source

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