Multilayer W-doped vanadium dioxide thermal sensors with extended operation region

Bolometers rely upon the temperature coefficient of resistance (TCR) of their underpinning sensing layer to detect infrared radiation. Vanadium dioxide (VO₂) exhibits a very large, but abrupt TCR associated with its monoclinic to rutile phase transition. W-doping of VO₂ lowers and broadens its transition temperature, and by combining multiple discrete W:VO₂ layers, a sensing layer can be created with an extended temperature operation region. Herein, we report such a multilayer W:VO₂ thin film by atomic layer deposition (ALD). The film displays an average TCR of -9.5 (±3.5) %K^-1 from 30°C to 60°C. A sensing layer consisting of 10 individual W:VO₂ layers is simulated with a multi-objective genetic algorithm (MOGA) for maximum average TCR (μ) and minimum variation (σ) across an extended target temperature range producing an optimized layer structure at max ( $\left|\mu \right|-\sigma$ ) with average TCR response of -6.7 (±0.9) %K^-1 from 20°C to 70°C. This work highlights the potential for the broader application of uncooled bolometers.