Alain Haché, Maryam Manafzadeh, Université de Moncton, New Brunswick, Canada
The optical characteristics of thin films can display remarkable sensitivity to the refractive index of the constituent material, making phase-change materials particularly interesting for sensing purposes. Among these materials, vanadium dioxide (VO₂) stands out for its exceptional performance. It undergoes significant shifts in refractive indices and electrical conductivity during its transition from insulator to metal, which occurs at approximately 70 °C, a temperature not far from room temperature. The versatility of VO₂ lies in its ability to undergo phase transition triggered by various stimuli including heat, light, and electric fields, enabling a broad range of sensor applications. One effective approach involves observing the interaction of light and infrared radiation with VO₂ films and analyzing the resulting alterations in amplitude and polarization states. These changes can be precisely measured using signal modulation and amplification techniques, facilitating the development of miniaturized sensors. Films as thin as 50 nanometers can be utilized in this setup. In this study, we outline and demonstrate methodologies employing VO₂ thin films to detect subtle fluctuations in temperature and electrical currents. The sensing mechanism capitalizes on the generation of heat through mechanical means, such as friction, or electrical heating via the Joule effect. The paper will discuss theoretical limits and provides proof of concept demonstrations.