Manufacture and characterization of sol-gel V_1-x-yW_xSi_yO₂ films for uncooled thermal detectors

V_1-x-yW_xSi_yO₂ films for uncooled thermal detectors were coated on sodium-free glass slides with sol-gel process, followed by the calcination under a reducing atmosphere (Ar/H₂ 5%). The V_1-x-yW_xSi_yO₂ films as prepared inherit various phase transition temperatures ranging from 20 to 70 °C depending on the dopant concentrations and the fabrication conditions. Compared to the hysteresis loop of plain VO₂ films, a rather steep loop was obtained with the addition of tungsten components, while a relaxed hysteresis loop with the tight bandwidth was contributed by Si dopants. Furthermore, the films with switching temperature close to room temperature were fabricated to one-element bolometers to characterize their figures of merit. Results showed that the V_0.905W_0.02Si_0.075O₂ film presented a satisfactory responsivity of 2600 V/W and detectivity of 9 × 10⁶ cm Hz^1/2/W with chopper frequencies ranging from 30 to 60 Hz at room temperature. It was proposed that with appropriate amount of silicon and tungsten dopants mixed in the VO₂, the film would characterize both a relaxed hysteresis loop and a fair TCR value, which effectively reduced the magnitude of noise equivalent power without compromising its performance in detectivity and responsivity.