Content area
Full Text
In this Letter thin films of zinc oxide (ZnO) are prepared by sol-gel method and deposited on glass substrate to evaluate structural and optical properties of the film. The films were grown at different thicknesses in the range of 100-180 nm. The properties of layers were characterised using X-ray diffractometer (XRD), atomic force microscope (AFM) and optical spectrophotometer to evaluate the quality of the thin film for photovoltaic applications. The results from XRD pattern revealed that the grown films exhibit wurtzite structure with (002) preferential plane. The results from AFM data revealed that the films had nano-sized grains with a grain size from ~25 to 60 nm depending on the film thickness. The optical spectrophotometer studies exhibited direct allowed transition with an energy bandgap of 3.12-3.02 eV for films with thicknesses of 100-180 nm, respectively. The refractive index as well as extinction coefficient of films was also measured.
(ProQuest: ... denotes formulae omitted.)
1. Introduction: In recent years zinc oxide (ZnO) films have been investigated as a transparent conducting oxide because of their good electrical and optical properties in combination with large bandgap and lack of toxicity [1], ZnO has a high dielectric constant and exciton induced in it has a strong binding energy, which gives them a long lifetime at room temperature. This material is an II-VI compound semiconductor with a wide variety of applications as electrodes, window materials in display, solar cells and various optoelectronic devices [2, 3]. Thus, accurate information about the structural and optical properties of the ZnO thin film is indispensable for the design and analysis of various optical and optoelectronic devices.
The optical and physical properties of ZnO thin films grown by a variety of deposition methods [4, 5] are affected by the substrate temperature, coating conditions, annealing and also film thickness [5, 6]. From the various methods of film preparation, the sol-gel method is more popular because of its cheapness, reliability, repeatability and simplicity. Certain applications require ZnO films with some specific structure characteristics, orientation, stress relief, smooth surface and high packing density. In the present work, these characteristics are examined as a function of the thickness of the film. It has been observed that the crystallite size and the density of film significantly increase with increase...