Optical and electrical properties of Al-doped ZnO thin films by atomic layer deposition
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Optical and electrical properties of Al-doped ZnO thin films by atomic layer deposition Yong Wu1, Fa Cao1, and Xiaohong Ji1,* 1
School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, China
Received: 21 January 2020
ABSTRACT
Accepted: 19 August 2020
The present work highlights the low temperature deposition of Al-doped ZnO (AZO) thin films by atomic layer deposition (ALD). The effects of Al doping concentration and substrate temperature on structural, electrical and optical properties of AZO thin films have been systematically studied. X-ray diffraction analysis demonstrates that the preferred orientation of AZO thin films alters from (100) to (002) with the increase of both substrate temperature and Al doping concentration, which may affect the electrical property of the AZO. The resistivity of the AZO reduces with increasing the temperature from 160 to 220 °C and then remains broadly stable (in the range of 220–260 °C), while the resistivity of the AZO thin films exhibits a sharp fall followed by a slow rise with Al concentration increasing from 0 to 3.57 at.% (atom %). The AZO film deposited at substrate temperature of 220 °C and Al content of * 2.17 at.% shows the lowest resistivity of 8.33 9 10–4 X cm and the high transmittance of * 95%, respectively. The work indicates a promising low temperature deposition of AZO thin films as transparent conductive oxide film.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction Recently, transparent conducting oxide (TCO) films have attracted significant notice for its wide applications in opto-electrical devices [1–6] such as liquid crystal displays (LCD), organic light-emitting diodes (OLED), thin film transistors (TFT), solar cells. Indium tin oxide (ITO), one of the conventional TCO film, has good electrical and optical properties (resistivity, q \ 10–3 X cm, transmittance [ 80% in the
Yong Wu and Fa Cao contributed equally to this article.
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10854-020-04292-9
visible region) [7]. However, the toxicity and scarcity of indium (In), and the lack of thermal stability and flexibility of ITO make exploring alternatives of ITO be significant. Al-doped ZnO (AZO) thin film is one of the most promising candidates because of its low price, non-toxicity and cost-effective properties. Furthermore, to be compatible with portable/flexible devices, such as plastic substrate, organic layers and the polymers thin films [8, 9], it is essential to obtain high transparent conductive AZO thin films at low temperature. The requirements of high-quality AZO
J Mater Sci: Mater Electron
in practical applications push forward the development of the fabrication techniques. Recently, atomic layer deposition (ALD), which is based on self-limiting adsorption effect on the surface, shows growing interest in the fabrication of AZO thin films due to its high controllability and low temperature deposition feature [10–12]. For example, Ban
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