Improving the ethanol sensing of ZnO nano-particle thin films—The correlation between the grain size and the sensing mechanism |
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Authors: | Thanh Thuy TrinhAuthor Vitae Ngoc Han TuAuthor VitaeHuy Hoang LeAuthor Vitae Kyung Yul RyuKhac Binh LeAuthor Vitae Krishnakumar PillaiJunsin YiAuthor Vitae |
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Affiliation: | a Information and Communication Device Laboratory, School of Information and Communication Engineering, Sungkyunkwan University, Republic of Korea b Department of Energy Science, Sungkyunkwan University, Republic of Korea c University of Sciences, Vietnam National University, Ho Chi Minh City, Vietnam |
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Abstract: | ZnO and Sn doped ZnO (ZnO:Sn) thin films at various doping concentrations from 1 to 10 at.% were prepared by the sol-gel method for an ethanol sensing application. The Sn doping significantly influenced the film growth, grain size and response of the films. The XRD patterns showed that the hexagonal wurtzite structure of the ZnO film was retained even after the Sn doping. The crystallite grain sizes of the ZnO:Sn thin films at 0, 2 and 4 at.% were estimated by using the typical Scherrer's equation. The crystalline quality of the films at 6, 8 and 10 at.% of Sn was degenerated. Typical FESEM images demonstrated the different morphologies for the ZnO:Sn thin films at various Sn concentrations; many pores of various dimensions were observed depending on the doping level. A TEM analysis of the ZnO:Sn thin films at 0, 2 and 4 at.% was performed to verify the grain size. The optimum Sn doping level of ZnO:Sn thin film for ethanol sensing was estimated to be 4 at.%. The 4 at.% sample obtained the highest response to ethanol vapor in the 10-400 ppm level range at a low operating temperature of 250 °C. The sensing mechanism was explained by a variation in the sensitivity model from a neck-grain-boundary controlled sensitivity to a neck-controlled sensitivity. Our work demonstrates the ability to reduce the working temperature as well as to increase the response of ZnO thin film based gas sensors to detect ethanol, which would be of great merit for commercialized applications. |
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Keywords: | ZnO:Sn thin films Neck-controlled sensitivity Ethanol sensing Sol-gel process |
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