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چکیده
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Zinc oxide (ZnO), an n-type semiconductor with direct band gap of 3.37 eV and excellent chemically stability has attracted much attention for its potential use as emitter in optoelectronic devices [1]. ZnO is also well suited to be used as conducting and transparent optical windows in photovoltaic solar cells because it satisfies the requirements for conductivity and transparency needed for this application [2]. In this paper we report the growth of the nanorod ZnO thin films on ZnO coated glass substrates by chemical solution deposition method. The diameter of the nanorod ZnO thin films was controlled by varying the precursor concentrations and the temperature of deposition. X-ray diffraction patterns and FE-SEM images show the nanorod ZnO thin films have hexagonal structure with c-axis oriented respect to the surface of substrate [3]. The nanorod ZnO thin films on the substrate have a diameter between 100-450 nm and a length at about 1 μm. The nanorod ZnO thin films had more than 85% transmittance in the visible region. The steep absorption edge of the films and FE-SEM images demonstrated a dense and uniform surface that was free of pits or pinholes with a narrow grain size distribution. The direct band gap energy (Eg) of as-deposited films ranged from 3.45 to 3.80 eV depending on precursor concentrations. This increase in Eg of deposited thin films can be assigned to the quantum size effect as expected from the nanorod nature of the ZnO thin films [4].
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