Effect of thickness on structural, optical, electrical and morphological properties of nanocrystalline CdSe thin films for optoelectronic applications

This paper presents effect of thickness on the physical properties of thermally evaporated cadmium selenide thin films. The films of thickness 445 nm, 631 nm and 810 nm were deposited employing thermal evaporation technique on glass and ITO coated glass substrates followed by thermal annealing in air atmosphere at temperature 300 degrees C. The as-deposited and annealed films were subjected to the XRD, UV-Vis spectrophotometer, source meter, SEM and EDS to find the structural, optical, electrical, morphological and compositional analysis respectively. The structural analysis shows that the films have cubic phase with preferred orientation (111) and nanocrystalline nature. The structural parameters like inter-planner spacing, lattice constant, grain size, number of crystallites per unit area, internal strain, dislocation density and texture coefficient are calculated. The optical band gap is found in the range 1.69-1.84 eV and observed to decrease with thickness. The electrical resistivity is found to increase with thickness for as-deposited films and decrease for annealed films. The morphological studies show that the as-deposited and annealed films are homogeneous, smooth, fully covered and free from crystal defects like pin holes and voids. The grains in the as-deposited films are densely packed, well defined and found to be increased with thickness. (C) 2015 Elsevier B.V. All rights reserved.