Controllable synthesis of Sn:ZnO/SnO 2 nanorods: pH-dependent growth for an ethanol gas sensor
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Controllable synthesis of Sn:ZnO/SnO2 nanorods: pH‑dependent growth for an ethanol gas sensor R. Mohamed1,2 · M. H. Mamat2,3 · M. F. Malek2,4 · A. S. Ismail3 · H. A. Rafaie1 · M. Rusop2,3 Received: 12 April 2020 / Accepted: 25 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Tin-doped zinc oxide/tin oxide nanorod (Sn:ZnO/SnO2 NR) films were successfully synthesized using a solution immersion method by manipulating the pH concentration of the solutions to fabricate an ethanol gas sensor. Sn:ZnO/SnO2 NR films were prepared at constant Sn:ZnO solution pH (5.5), while the pH of the SnO2 solutions was varied between 4.5 and 6.5. In this study, the structural, morphological, and optical properties of Sn:ZnO/SnO2 NR films were investigated. The diameter and thickness of Sn:ZnO/SnO2 NR films were found to increase with the S nO2 pH. Interestingly, the Sn:ZnO/SnO2 NR sample that was prepared at SnO2 solution pH 5.5 showed the highest relative peak intensity along the c-axis plane orientation, which enhanced the sensor performance due to the shorter carrier pathway. In addition, this sample indicated a higher level of surface donor-related defects, which are favorable for sensing device performance. The samples were exposed to ethanol gas to measure their gas-sensing properties. Sn:ZnO/SnO2 NR films prepared at S nO2 solution pH 5.5 showed the highest sensing performance with short response/recovery times.
1 Introduction Metal oxide materials in one-dimensional (1D) nanostructures have gained great attention among researchers for nano-device applications. In sensor application, 1D nanostructures are prudent and highly favorable to enhance the performance of a gas sensor. These 1D nanostructures have a small crystal structure, extraordinarily high surface area,, and a high density of active sites on the surface, which will grant more gas reaction with a sensing material [1]. Metal oxide in nanorod (NR) structures is of interest due to its * R. Mohamed [email protected] * M. F. Malek [email protected] 1
Faculty of Applied Sciences, Universiti Teknologi MARA Pahang, 26400 Bandar Tun Razak Jengka, Pahang, Malaysia
2
NANO‑SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia
3
NANO‑ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia
4
Faculty of Applied Sciences, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia
special characteristics and potential to be used in many electronic devices. The thin and vertical NR structure has shown less agglomeration due to its larger dimensions. Thus, more tested gas is adsorbed and diffused quickly on the sensor surface, which contributes to the enhancement of the sensing performance [2, 3]. Among metal oxides, ZnO and SnO2 have been shown to be good sensing materials to sense oxidizing and reducing gases at low working temperatures [4]. Their good electr
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