Nano-vanadium oxide thin films in mixed phase for microbolometer applications

Abstract

Among the several phases of vanadium oxide, mixed phases of VO2 and V2O5 are preferred for uncooled micro-bolometers with low noise. The aim of this investigation is to achieve mixed phase VO2 and V2O5 thin films with nanometre grain sizes and high temperature coefficient of resistance (TCR). Since the phase depends upon the oxygen reactivity, these vanadium oxide thin films are prepared by reactive electron beam evaporation at different oxygen flow rates and substrate temperatures. The mixed phases have been evaluated through x-ray diffraction and x-ray photo emission studies. The temperature dependence of resistance has shown that the films grown at 473 K with 2.8 × 10−5 mbar chamber pressure of oxygen (VO2 : V2O5 ratio of 36 : 64) have the highest TCR of −3.2 K−1 with a reasonable low resistance (120 Ω/square).