The evolution of nanoscale pores with post-annealing and the structure-electrical property correlation in vanadium oxide thin films

Abstract

Structure-property correlation in vanadium oxide nanoscale thin films used in uncooled thermal detectors is a crucial question for device performance. The purpose of this work is to investigate the evolution of the nanoscale pores with post-annealing temperature and its correlation to electrical properties. It is observed that the as-deposited film has an amorphous matrix containing nanoscale crystal grains of VO2, V2O5, and V6O13 phases, and additionally nanoscale fibrous-like pores. The film post-annealed at 200 C under high purity N2 atmosphere for 3 h possesses nanoscale crystal grains predominantly with the VO2 phase besides V6O13 and nanoscale spherical pores. After post-annealing at 300 °C, a clear enhancement in crystallinity and diminishing of amorphous structure has been found, and the film contains VO2, V2O3, and V6O13 phases, additionally larger pores and cracks. The electrical resistance and temperature coefficient of resistance increase with increasing temperature, whereas the electrical noise reduces after annealing at 200 °C and increases again at 300 °C. The best combination of values for 1/f noise corner frequency (5.7 kHz), electrical resistance (90 kΩ), and temperature coefficient of resistance (-2.71 %K−1) is obtained for the film after post-annealing at 200 °C, favorable for application.