Ferroelectric film thickness dependence of properties of infrared detector with an SiO₂ aerogel thermal insulation layer

The variation of voltage responsivity of infrared detectors and other parameters of the devices with the thicknesses of the ferroelectric film was studied. The thermal insulation layer of the detector was sol-gel derived porous silica. The absorption, pyroelectric coefficient and thermal conductance of the devices were found to increase with the increase of the ferroelectric film thicknesses. The thermal conductance of the devices with 240 nm ferroelectric film was about the same order as those devices with microbridge structure, e.g. 10^-7 W/K. This result demonstrates that high quality of infrared detector can be made with an aerogel silica thermal insulating layer. The degradation of the voltage responsivity with the increase of film thickness is due to the rapid increase of the thermal conductance. The repeated high temperature annealing processes at 650°C during the preparation of the ferroelectric film may cause a decrease in the porosity of the silica.