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Growth and transport properties of nanocrystalline CdS thin film

R. DEVI1,* , P. K. KALITA2, P. PURAKAYASTHA2, B. K. SARMA1

Affiliation

  1. Department of Physics, Gauhati University, Guwahati-781 014, India
  2. Department of Physics, Guwahati College, Guwahati-781 021, India

Abstract

Cadmium Sulphide (CdS) nanoparticles were synthesized by a chemical route using organic substance as the desired matrix at room temperature 300K. The crystallite sizes of the films are determined from X-ray diffraction lines. The optical band gap ‘Eg’of the CdS films are determined from the UV absorption spectroscopy and are found to be 2.9 eV. The current-voltage curve of the films are drawn and temperature-dependent conductivity (300-523K) are found out to be of the order of 10-5 – 10-6 ohm-1 cm-1. The “as deposited” films are annealed in air at 523K for 2 h and the effect of annealing on structural, morphological, optical and electrical properties are studied. The annealed films show a ‘redshift” of 0.6 eV in their optical band gap ‘Eg’. After annealing, the diffraction peaks in the XRD pattern become sharp with high intensity and the crystallites’ size increases from 10 – 39 nm, which results in a increase in electrical conductivity. From the conductivity measurement at different temperatures, for fresh and annealed films, the activation energy of the films were calculated and found to be between 0.30 - 0.57 eV for low temperature regions and between 1.24 - 1.34 eV for high temperature regions..

Keywords

Chemical method, UV spectra, Energy band gap, Activation energy, CdS, Nanocrystals.

Submitted at: March 7, 2008
Accepted at: Nov. 11, 2008

Citation

R. DEVI, P. K. KALITA, P. PURAKAYASTHA, B. K. SARMA, Growth and transport properties of nanocrystalline CdS thin film, Journal of Optoelectronics and Advanced Materials Vol. 10, Iss. 11, pp. 3077-3082 (2008)