Wide-temperature (up to 100 degrees C) operation of thermostable vanadium oxide based microbolometers with Ti/MgF2 infrared absorbing layer for long wavelength infrared (LWIR) detection

Abstract

A strategy for a microbolometer operating over a wide range of temperatures up to 100 degrees C with low nonlinearity and without hysteresis is described, based on a thermally stable VO2(B) film and 5-stack Ti/MgF2 infrared (IR) absorbers. The highly crystalline VO2(B) film formed on an amorphous SrTiO3 layer shows a high temperature co-efficient of resistivity and low resistivity without any significant changes up to 100 degrees C. No significant changes are observed in the two values even after keeping the film at 100 degrees C for over a month. This outstanding thermostability makes the microbolometers with and without the IR absorber easily capable of operating up to 100 degrees C. The microbolometers with the 5-stack Ti/MgF2 IR absorber also shows increases in its responsivity by 4 times at 20 degrees C and by 3 times at 100 degrees C compared to that without IR absorber due to the increase of IR absorption. These results are achieved without significant increase in the thermal time constants even with the introduction of thermally massive IR absorber.