Structural and Optical Properties of Calcium-doped Zinc Oxide Thin Film Deposited by the PLD Method

Abstract

Abstract: A sample of calcium-doped zinc oxide (CZO) thin films of varying thicknesses were prepared by the pulsed laser deposition technique (PLD) on glass substrates. The film samples were grown at constant oxygen pressure. The pulsed laser deposition target used was Ca-doped zinc oxide 3 at. % nanopowder synthesised by a modified sol-gel process. The structural, morphological and optical properties of the CZO thin film were studied. From the X-ray diffraction analysis, the orientation of Ca-doped zinc oxide thin films was found to be along the c-axis, displaying only a (002) diffraction peak. The X-ray diffraction spectra revealed that the crystalline quality of the film was enhanced and grain size grew by increasing the film thickness. Cross-sectional microscopy images show the formation of columnar structure in the obtained thin film with low surface roughness when the film thickness increases. CZO thin film is highly transparent in the visible wavelength region with a transmittance higher than 90% for the lowest thickness. The calculated optical band gap is approximately 3.4 eV. The obtained results revealed that our samples are promising as transparent conducting oxide layers in many technological applications.

Keywords: Ca-doped ZnO nanoparticles, Sol-gel, PLD, Thin films, Optical properties.