Annealing temperature effect on the temperature coefficient of resistance for vanadium oxide (VOx) thin films as bolometer materials

Vanadium oxides (VOx) are representative materials with a high temperature coefficient of resistance (TCR); however, VOx films can have complex phase structures that are dependent on their fabrication method. While past research has focused on the TCR behavior of VOx thin films, this study investigates the TCR of VOx thin films annealed at different temperatures as well as focuses on the relation between the VOx phase, surface morphology, sheet resistance, and TCR. VOx thin films were deposited via radio-frequency magnetron sputtering and annealed at 150 °C-500 °C in 20% O₂. Alongside morphological changes, the deposited VOx thin films exhibited phase changes from V₂O₅ to VO₂ with increasing annealing temperature. The VOx thin films annealed at 300 °C and 330 °C showed the lowest and highest average TCR of 1.25%/°C and 3.34%/°C, respectively. Furthermore, a bolometer fabricated using the higher-TCR film showed more than 5-fold infrared responsivity under the same infrared intensity.