Influence of process parameters and characterization of niobium-doped vanadium oxide thin films for microbolometers

Vanadium oxide (VO_x) is the mainstream sensing material for uncooled microbolometers due to its high temperature coefficient of resistance (TCR), low noise, and low thermal conductivity. However, intrinsic limitations such as a large thermal hysteresis, a high metal-insulator transition (MIT) temperature (~68 °C), and elevated sheet resistance hinder further improvements in device sensitivity and stability, motivating the exploration of new material compositions. This work investigates niobium (Nb) as a dopant to overcome these limitations. Nb-doped VO_x thin films were fabricated via reactive co-sputtering, where the Nb content was controlled by varying RF power on an Nb target while keeping the DC power on a V target constant. By systematically investigating the influence of Nb content and O₂ partial pressure, a high TCR of -2.94%/°C was achieved under optimized conditions of 4.99% Nb content and 5% O₂ partial pressure, demonstrating the potential of Nb-doping for enhancing microbolometer performance.