Non-hysteretic branches inside the hysteresis loop in VO2 films for focal plane array imaging bolometers

In the resistive phase transition in VO2, temperature excursions from points on the major hysteresis loop produce minor loops. We have found that for sufficiently small excursions these minor loops degenerate into single-valued, non-hysteretic branches (NHBs) having essentially the same or even higher temperature coefficient of resistance (TCR) as the semiconducting phase at room temperature. We explain this behavior and discuss the opportunities it presents for infrared imaging technology based on resistive microbolometers. It is possible to choose a NHB with 100 to 1000 times smaller resistivity than in a pure semiconducting phase, thus providing a microbolometer with low tunable resistivity and high TCR.