Effect of pH on the crystallite size, elastic properties and morphology of nanostructured ZnS thin films prepared by chemical bath deposition technique

Abstract

Zinc Sulphide thin films have been fabricated on glass substrate via chemical bath deposition technique using zinc acetate, thiourea as the precursor of zinc and sulfur and ammonia for varying pH. The X-Ray diffraction patterns indicate the nanocrytalline nature of the films with broadening of diffraction peaks. Effective Mass Approximation, Scherrer Method and Williamson-Hall plots have been employed for determining crystallite size. The calculated crystallite sizes correlate well with the estimated crystallite sizes from High Resolution Transmission Electron Microscopy images. The HRTEM images show clear lattice fringes of nanocrystallites overlapping each other with random orientations. The elastic properties such as lattice strain, stress and energy density of ZnS thin films have been calculated from the modified form of Williamson-Hall analysis namely Uniform Deformation Model, Uniform Stress Deformation Model, and Uniform Deformation Energy Density Model. The Scanning Electron Microscope images indicate the granular texture of synthesized ZnS thin film at pH 9.6 and coagulation of granules into larger one with increase of pH. The results reveal the obvious effect of ammonia concentration on the optical properties, crystallite size, elastic properties and morphology of the surface of the films.