Low-temperature vanadium dioxide for CMOS integration and flexible polyimide applications

Vanadium dioxide (VO 2 ) is a popular phase-transition material with broad applications ranging from thermal management in smart windows to neuromorphic computing. Currently, VO 2 thin films are usually fabricated at high temperatures, making them incompatible in forming on top of CMOS and flexible polyimide substrates. This study explores a low-temperature VO 2 thin film formation approach that combines atomic layer deposition (ALD) with a post-deposition anneal. With systematic material characterizations, we clearly demonstrate high-quality VO 2 film formation on Si substrates at a significantly reduced annealing temperature of 300 °C. Further reducing the annealing temperature to 250 o C is shown to lead to insufficient VO 2 crystallization whilst elevating the temperature to 400 o C results in overoxidation into V 2 O 5 . We implement our method on polyimide substrates and demonstrate that the high-quality phase transition is indeed preserved. This work demonstrates the ability of low-temperature formation of VO 2 thin films, and it will accelerate the adoption of VO 2 in emerging electronic devices as well as photonic applications.