Effects of temperature and doping concentration on the piezoresistive property of vanadium dioxide thin film

Abstract

Vanadium dioxide (VO 2 ) is a phase transition material whose physical and electrical properties, such as resistance, significantly change at the critical temperature. Specifically, the piezoresistive property and, thus, the gauge factor may change considerably in VO 2 thin films; however, studies focusing on this phenomenon remain limited. This study evaluated the gauge factor of VO 2 thin films by varying the temperature and W doping concentration. VO 2 films were deposited on a conventional Si wafer using the sol-gel method, followed by an annealing process. Samples were produced without W doping and with 0.3, 0.6, and 1.0 at% doping concentrations. Phase transitions were observed via resistance changes of one order of magnitude near-critical temperatures of ∼60 °C for no doping, ∼50 °C for 0.3 at%, and ∼30 °C for 0.6 at%; the sample with a 1.0 at% concentration exhibited a linear resistance change, resulting in no phase transition. The X-ray diffraction pattern shifted with the temperature change and showed critical temperatures similar to those obtained from the resistance measurements. Additionally, the temperature dependence of the gauge factor was experimentally obtained based on the carrier concentration and mobility. The gauge factors obtained experimentally and those calculated from the carrier concentration and mobility were examined. A gauge factor of 350 was obtained, much larger than that of the conventionally used Si, near the critical temperature at each doping concentration. The feasibility of VO 2 thin films as piezoresistive materials was thereby demonstrated. • The gauge factor of VO 2 thin films by varying the temperature and W doping concentration was evaluated. • The temperature dependence of the resistances, XRD patterns, gauge factors, carrier concentrations, and mobilities were experimentally evaluated. • A gauge factor of 350 was obtained near the critical temperature at each doping concentration.