Preparation of atomic layer deposited vanadium dioxide thin films using tetrakis(ethylmethylamino) vanadium as precursor

Abstract

Vanadium dioxide (VO2) thin films were deposited by atomic layer deposition (ALD) using a tetrakis(ethylmethylamino) vanadium precursor and an H2O oxidant at a temperature of 150 °C. Optimization of postdeposition annealing results in smooth, continuous VO2 films (thickness, t ∼ 30 nm) with small grains, exhibiting a transition from semiconducting to metal phase, typically known as the metal-insulator transition (MIT), at ∼72 °C with a switching ratio of ∼102. Such films were produced with high repeatability on a wafer scale and have been successfully utilized in resistively coupled oscillators and self-selected resistive devices. Under a smaller process window, thin films (t ∼ 30 nm) with very large grains have also been produced, exhibiting the MIT ratio of ∼103, which is the highest achieved for the ALD VO2 films deposited on SiO2 substrates. Both types of films were characterized again after 120 days to access their stability in air, a property that was rarely investigated.