Application of mesoporous TiO₂ as a thermal isolation layer for infrared sensors

An ordered, mesoporous TiO₂ thin film could possibly enhance the efficiency of a microbolometer when used as a thermal isolation layer. The infrared transmission characteristics of a 150 nm thick mesoporous TiO₂ film were measured by FT-IR. The calculated infrared absorption rate was higher than 85% in the 8-12 μm wavelength region. The thermal conductivity of a mesoporous TiO₂ film was measured by the 3ω method. The CFD-ACE program was used to simulate the thermal isolation effect of a mesoporous TiO₂ film inserted in a microbolometer structure. The simulation shows that a great enhancement in the thermal insulation was obtained by using a mesoporous TiO₂ layer. The mesoporous TiO₂ thin film effectively blocks heat flow from TiN absorber to the bottom layer and returns the downstream heat to the upper resistor layer.