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Preparation of CuO thin films by thermally oxidized metallic Cu films for CdS/CuO heterojunction diode
Author(s)
Wongcharoen, Ngamnit
Gaewdang, Thitinai
Date Issued
January 1, 2017
Type
Article
Abstract
Copper thin films were deposited on glass substrates using thermal evaporation in vacuum and then thermally oxidized in air at temperatures of 100-500°C. XRD patterns showed the formation of a fine grain Cu2O phase at 300°C and a CuO phase at 400°C, respectively. Crystallinity and grain size improved with increasing oxidation temperature. The energy gap of the samples evaluated from absorption measurements was 2.10-2.23 eV. Important electrical parameters of the CuO thin films obtained from oxidizing at 500°C were resistivity of 8.53x103 Ω•cm, carrier concentration of 7.60x1013 cm-3, and mobility of 6.22 cm2/V•s. A prototype of a CdS/CuO thin-film heterojunction diode was successfully prepared by thermal evaporation of CdS thin films on CuO thin-film substrate in a vacuum. The obtained device exhibited a good rectifying behavior from I-V characteristics. Junction parameters calculated using I-V data were barrier height of 5.190 eV, ideality factor of 0.520, and series resistance of 3.87 O. Impedance spectroscopy of the device was investigated at temperatures of 25-60°C. The real and imaginary parts of the complex impedance changed with the temperature and frequency. The experimental results suggested that the device was a good candidate for photovoltaic devices with low thermal budget and low product cost.
Citation
Chiang Mai University Journal of Natural Sciences, 16(1), 63-76, 2017