Fabrication of V1−x Ti x O2 microbolometers on Si3N4/SiO2 membranes

Abstract

V1−x Ti x O2 thin films have been prepared on Si3N4/SiO2/Si substrates by the two-step process of (1) growth of VO2/TiO2 thin films by metal-organic decomposition with carbothermal reduction, and (2) the interdiffusion between V and Ti atoms at the interface between the VO2 and TiO2 thin films during the growth of the VO2 thin film. The abrupt resistance change and the thermal hysteresis due to the metal-insulator transition were gradually suppressed with increasing the firing temperature, and they completely disappeared for the V0.65Ti0.35O2 thin film prepared at 650 °C. A relatively high TCR of −4.2%/K was obtained from the film over a wide temperature range of 20 °C–90 °C. V0.65Ti0.35O2 microbolometers with a size of 5 μm × 15 μm were fabricated by photolithography and Ar ion milling, and a Si3N4/SiO2 membrane under the microbolometer was formed with an aqueous KOH solution. The DC sensitivity of the fabricated microbolometer on the membrane was estimated to be 9876 W−1 and 20 times higher than that of the microbolometer on the Si3N4/SiO2/Si substrate. The V0.65Ti0.35O2 microbolometer on the membrane is available for a terahertz detector operating over the wide temperature range.