Simulation of spectral emissivity of vanadium oxides (VO_x)-based microbolometer structures Available to Purchase

A simulation of room temperature spectral emissivity of an industry standard VO_x-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 VO_x, 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 VO_x, 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 VO_x/Si₃N₄/Air/Al/Si system. Calculations show that the Si₃N₄ layer provides the much-desired linear performance of the VO_x-based microbolometer.