Investigations into the influence of temperature on the optical properties of NiO thin films

Abstract

Nanocrystalline thin films of nickel oxide (NiO) have been deposited on glass substrates in polyvinylpyrrolidon (PVP) matrix solution by chemical bath deposition technique. The films have been annealed at 373 K–573 K and changes in their optical properties have been studied. Investigation reveals that the optical properties of the films have been irregularly influenced by heat treatment. They show varied transmittance for different annealing temperatures making them useful for applications in optoelectronic devices. The structural property of the films has been obtained by means of X-ray diffraction (XRD), while the elemental composition has been deduced from Rutherford back scattering spectroscopy (RBS). XRD analyses of the film annealed at 375 K show that the films are crystallized and have rhombohedral structure. The crystallite size of the film has been determined and found to be 89.90 nm. The films band gaps range from 2.30 eV – 2.95 eV, which are lower than that of their solid materials. This however makes them useful for antireflection coatings and other applications.