Monolithic pyroelectric infrared detectors using SiO2 aerogel thin films

The effects of SiO2 aerogel film thickness on the properties of pyroelectric device were studied by ANSYS thermal simulation and infrared radiation test. At first, the temperature distributions of the pyroelectric devices with different thicknesses of SiO2 aerogel film were simulated by ANSYS. After that, aerogel films with thicknesses from 300 nm to 1000 nm were deposited on Si substrates by spin coating. Thermal conductivity of SiO2 aerogel film was 2.78 × 10−2 W/m K by 3ω method test. Films were utilized in our pyroelectric infrared detectors as thermal insulators. The detectivity (D*) of these detectors was measured by mechanically chopped blackbody radiation. The D* values was enhanced as the SiO2 aerogel film thickness increased from 300 nm to 800 nm, indicating the thermal isolation effects was improved. Detector with thermal insulation layer thickness of 780 nm possessed the greatest D* over the whole frequency range from 5.3 Hz to 133.3 Hz. The D* was above 7 × 107 cm Hz1/2 W−1 and reached the highest value of 9.7 × 107 cm Hz1/2 W−1, which represented a wide bandwidth of over 128 Hz. This result indicated that SiO2 aerogel film of 780 nm in thickness was a promising thermal isolation material for monolithic pyroelectric infrared detectors.