Optimization of temperature coefficient of resistance of Al-doped vanadium oxide thin film prepared by atomic layer deposition for uncooled microbolometer

Vanadium oxide (VO_X) is an excellent thermal sensitive candidate for uncooled microbolometers. However, undoped VO_X prepared by atomic layer deposition (ALD) has a temperature coefficient of resistance (TCR) of ca. ?2 ～ ?3%/K. For improving its TCR, our deposition approach based on the combination of ALD and rapid post-deposition annealing (RTA) is proposed. Besides, aluminum-doping into the VO_X films is performed via that approach, and the number of Al₂O₃ cycles is adjusted for varying the dopant loadings. Changes in physical, chemical, and electrical characteristics of the VO_X films due to Al-doping are discussed in detail. The advantage of introducing Al³⁺ dopants is to hinder the thermally activated phase transition of VO₂ phases, leading to an improvement in TCR of Al-doped VO_X up to ?4.2%/K, which remains stable over a wide temperature range of 298–328 K. However, the excessive Al doping also carries an adverse effect on TCR. The reason for that is discussed for further understandings of doping effects.