Influence of annealing processing on dissipation electrical energy, volume, and surface energy loss functions of CZO fil
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ORIGINAL PAPER
Influence of annealing processing on dissipation electrical energy, volume, and surface energy loss functions of CZO films P Abbasi and V Dalouji* Department of Physics, Faculty of Science, Malayer University, Malayer, Iran Received: 06 December 2019 / Accepted: 17 March 2020
Abstract: The present study was conducted to investigate the optical constants of copper (Cu)-doped zinc oxide (ZnO) films annealed at different temperatures. The absorption coefficient of the films increased by changing the annealing temperature. The lattice dielectric constant eL , concentration of the free-charge carriers, plasma frequency, Spitzer–Fan model, and the waste heat of electrical energy in the films were analyzed using the refractive index n and extinction coefficient k spectra. The results of the study showed that changing the annealing temperature values significantly influences the refractive index and extinction coefficients of CZO films. The increase in the electrical susceptibility vc in annealed films can be due to the increased concentration of free-charge carriers in these films. The maximum electrical energy loss (tan d) in the films as a function of photon energy occurred at 400 °C. The as-deposited films showed minimum volume and surface energy loss functions in their range of optical band gaps. The variations in the phase and group velocity of the films with post-annealing temperature were consistent with the variations in the reduction of the density of freecharge carriers for these films. Films annealed at 600 °C had the maximum root mean square roughness of about 5.62 nm. Films annealed at 400 °C had the maximum extinction coefficients k such that they increased for all ranges of wavelength. vc had the maximum values in the films annealed at 600 °C, for all ranges of wavelength, and they increased by increasing the wavelength. The increase in vc of the films annealed at 600 °C can be attributed to the increase in the density of freecharge carriers in these films. Keywords: Optical constants; Spitzer–Fan model; Energy loss; CZO thin films PACS Nos.: 77.55.hf; 78.66.Bz; 78.68.?m
1. Introduction Recently, thin-film materials have attracted a great deal of attention due to their high technological applications in fields such as chemistry and physics [1–5]. The surface morphology of the films plays an important role in the nanotribology, chemical reactions, and thermodynamics of surfaces at microscopic and macroscopic length scales, and it also has a major role in the optical and structural properties of the films [6–12]. Zinc oxide (ZnO), as a II–VI semiconductor with a direct large band-gap energy of (3.37 eV) and the large exciton binding energy of (60 meV) at room temperature, has been extensively investigated in various applications,
*Corresponding author, E-mail: [email protected]
for example, as a mid-layer in thin-film solar cells, optoelectronics, transparent conductive oxide (TCO) film transistors, and biosensors [13–17]. Due to their superior properties such as high crystalline quality,
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