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Pressure and Thickness Dependence of Physical Properties of ZnO:Ga Thin Films by Radio Frequency Magnetron Sputtering
Fang-Hsing Wang1* and Hua-Tz Tzeng2
1Department of Electrical Engineering, National Chung-Hsing University, Taichung 402, Taiwan, R.O.C.
2Graduate Institute of Optoelectronic Engineering, National Chung-Hsing University, Taichung 402, Taiwan, R.O.C
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Abstract:
Indium-free transparent conducting oxide films have attracted extensive attention in the field of optoelectronics. Ga-doped ZnO (GZO) thin films are deposited by radio frequency magnetron sputtering on glass substrates at a temperature of 200 °C with ZnO:Ga2O3 (3 wt%). The structural, electrical, and optical properties of the GZO thin films were investigated in terms of deposition pressure and film thickness variations. X-ray diffraction analysis showed that all the prepared GZO films exhibited hexagonal wurtzite crystal structure with a (002) preferential orientation along the c-axis, regardless of pressure and thickness. The average visible transmittance (including the glass substrate) in a wavelength range of 400–700 nm decreased with increasing thickness but varied less with pressure. The highest average visible transmittance reached 88.4% at the thickness of 150 nm and the pressure of 5 mTorr. The optical band gap of the GZO films calculated using Tauc’s method was in the range of about 3.6–3.9 eV. The resistivity of GZO thin films decreased with decreasing deposition pressure and increasing film thickness, and the minimum resistivity obtained at 5 mTorr and 1000 nm was 3.36 × 10-4 Ω-cm. The maximum figure of merit (FOM) of 3.09 × 10-2 Ω-1 was achieved at 5 mTorr and 1000 nm. The superior optical and electrical properties and high FOM show that the prepared GZO thin films are suitable for transparent conducting films and optoelectronic devices.
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Keywords: Ga-doped ZnO (GZO), Pressure, Thickness, Transparent conducting oxide (TCO), Magnetron sputtering
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Received:N/A; Revised:N/A; Accepted:N/A; Published:June 30, 2022
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*Corresponding author; e-mail: fansen@dragon.nchu.edu.tw
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Citation:Wang, F.H.; Tzeng, H.T.Pressure and Thickness Dependence of Physical Properties of ZnO:Ga Thin Films by Radio Frequency Magnetron Sputtering. Applied Functional Materials 2022, 2, 26-34. https://doi.org/10.35745/afm2022v02.02.0005
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Copyright: ©
2022
The Author(s). Published with license by IIKII, Singapore. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (CC BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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