Ultra-Thin Film Metallic Absorbers for Amophous Silicon Microbolometers: A Comparative Study

Uncooled microbolometers use an ultra-thin metal layer to absorb the incoming longwave infrared (LWIR) radiation. In this paper, ultra-thin films of Nb, NiCr, Ti, and Zr are considered and examined as IR absorbers for an amorphous silicon (a-Si) microbolometer. The optical absorptance of a quasi Fabry-Perot cavity microbolometer configuration is analyzed as a function of the absorber metal thickness and the cavity’s air gap thickness. Absorber thin films of Ti and Zr achieved the highest absorptance %, compared to NiCr which is typically used as an absorber in amorphous silicon (a-Si) microbolometers. Zr thin films, never considered before as IR absorbers, can be effective IR absorbers for LWIR microbolometers.