Preparation and properties of a thermal insulating layer and a buffer layer for multilayer pyroelectric film infrared detector

A thermal insulating layer and a buffer layer play a key role in the multilayer pyroelectric thin film infrared detector. In this work, a porous SiO₂ film serving as thermal insulating layer and a dense SiO ₂ film serving as buffer layer were prepared by sol-gel method. The porosities of the porous film and the dense film are about 50% and 6%, respectively. Maximum thickness values of a single layer porous film and that of a single layer dense film all come up to 1.5 μm. Rms (root-mean-square) surface roughness of the porous film is about 40 nm and that of the dense film is about 1.5 nm. Experimental result shows 0.4 μm dense SiO₂ film can flatten rough surface of the porous SiO₂ film, and the rms surface roughness is less than 5 nm. The composite SiO₂ film can effectively block thermal diffusion.