Citation: Azad, S.; Gajula, D.; Prio, M.H.; Koley, G. Effect of Strain on Properties of Metal Doped VO 2 Based Thermal Sensors on Muscovite Substrate. Eng. Proc. 2022, 27, 80. https://doi.org/10.3390/ecsa- 9-13320 Academic Editor: Jean-marc Laheurte Published: 1 November 2022 Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Proceeding Paper Effect of Strain on Properties of Metal Doped VO 2 Based Thermal Sensors on Muscovite Substrate † Samee Azad 1, *, Durga Gajula 2 , Makhluk Hossain Prio 1 and Goutam Koley 1 1 Holcombe Department of Electrical and Computer Engineering, Clemson University, Clemson, SC 29634, USA 2 Georgia Institute of Technology, Atlanta, GA 30332, USA * Correspondence: sameea@clemson.edu † Presented at the 9th International Electronic Conference on Sensors and Applications, 1–15 November 2022; Available online: https://ecsa-9.sciforum.net/. Abstract: In this work, VO 2 based thermal sensing thin film synthesized on flexible muscovite substrates by direct oxidation of deposited vanadium metal, were investigated for the impact of doping and strain on their electrical properties. We investigated both undoped and Ti doped VO 2 on muscovite substrate and compared with those on Quartz substrate. Both doped and undoped VO 2 were found to undergo phase transition due to effect of heat as well as mechanical strain on muscovite substrate. On the other hand, the Ti doped VO 2 , on both quartz and muscovite substrate showed significant reduction in the transition temperature compared to the undoped VO 2 thin films on these two substrates. When subjected to mechanical strain, the VO 2 thin film on muscovite substrates resulted in a decrease or an increase in resistance depending on whether the applied strain was tensile or compressive, respectively. The resistance change was also steeper around the transition temperature compared to room temperature, exhibiting high gauge factor. This metal doped VO 2 on flexible muscovite substrate has the significantly low transition temperature which causes the VO 2 film to undergo phase transition at a near-room temperature and enables it to be used as a temperature sensor with enhanced sensitivity. Keywords: VO 2 thin film; transition temperature; flexible substrate; mechanical strain; tensile strain; compressive strain; gauge factor 1. Introduction VO 2 has many important applications because of its uniquely reversible phase tran- sitioning properties [1–4]. There have been numerous studies reported on synthesizing high quality VO 2 on different substrates and their electrical and optical properties have been investigated in detail. While traditionally VO 2 is grown on sapphire, Si or quartz substrates, its synthesis on muscovite substrate has attracted special attention due to the optical transparency and flexibility of muscovite, which not only offers the possibility of modulating the optical properties of the transmitted light through phase transition but can enable the phase transition by application of mechanical strain. However, the typical transition temperature of 67 ◦ C is not low enough to induce phase change by application of strain, in unheated substrates, which can enable a host of applications requiring high sensitivity associated with the phase change region. Therefore, reduction in the transition temperature of the VO 2 is very much desired, which will make the VO 2 thin film will be more sensitive to physical parameters such as temperature, strain or electric field even at room temperature without any need for heating, enabling it to be used as a thermal sensor with great sensitivity. This can be achieved by doping the vanadium with metallic dopants such as W, Ti and Cr, which can reduce the transition temperature of VO 2 thin films [5,6]. In our previous reports [7,8] we have demonstrated the synthesis and properties of VO 2 synthesized on various substrates, including piezoelectric and flexible ones. We Eng. Proc. 2022, 27, 80. https://doi.org/10.3390/ecsa-9-13320 https://www.mdpi.com/journal/engproc