Simulation of spectral emissivity of vanadium oxides (VOx)-based microbolometer structures

Abstract

A simulation of room temperature spectral emissivity of an industry standard VOx-based microbolometer structure, with x equal to 1·8, is presented in this study. The simulation is based on Multi-Rad, a package that implements thin film optics in the form of matrix method of multilayers and assumes the layers to be optically smooth, parallel to each other and optically isotropic. The simulated results are shown to be in good accord with the available experimental data in the literature. The calculations show that bare VOx, that is VO2, V2O3 and V2O5, with different thicknesses, exhibits wavelength-dependent emissivity that scales almost linearly with thickness. In the wavelength range of 8–14 µm, the spectral emissivity of bare VOx, consisting of the stacked layers of the thin films of VO2, V2O3 and V2O5, of total thickness of 500 Å, behaves as a mixed system. The Si3N4 overlayer does not change the spectral emissivity of Al/Si while it decreases the spectral emissivity of the VOx/Si3N4/Air/Al/Si system. Calculations show that the Si3N4 layer provides the much-desired linear performance of the VOx-based microbolometer.