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

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 degrees C. Optimization of postdeposition annealing results in smooth, continuous VO2 films (thickness, t similar to 30nm) with small grains, exhibiting a transition from semiconducting to metal phase, typically known as the metal-insulator transition (MIT), at similar to 72 degrees C with a switching ratio of similar to 10(2). 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 similar to 30nm) with very large grains have also been produced, exhibiting the MIT ratio of similar to 10(3), 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.