Exploration of VO₂ Thin Films with Oxygen Deficiency

VO₂ has captured the attention of researchers due to its thermochromic properties and rapid semiconductor-to-metal transition. The semiconductor-to-metal shift occurs within the monoclinic M1 phase around 343K, coupled with a transformation from monoclinic to rutile crystal structure. The transparency of the monoclinic phase to near-infrared (NIR) radiation stands in contrast to the NIR opaqueness of the rutile phase. Maintaining precise stoichiometry in VO₂ is crucial, as even slight adjustments in oxygen levels can lead to the stabilization of different VO₂ polymorphs. Additionally, fine-tuning the stoichiometry offers a means of controlling the characteristics of VO₂. With this motivation, we have prepared stoichiometric and oxygen deficient VO₂ thin films on differently oriented sapphire substrates by radio frequency (RF) sputtering technique. The stoichiometric VO₂ thin films depicted characteristic semiconductor to metal transition around 343K. We noticed a complete suppression of semiconductor to metal transition in oxygen deficient VO₂ thin films and a metallic behavior was seen throughout the studied temperature range i.e. 273K to 373K. Oxygen deficiency led to significant modifications in the structural, electronic and optical properties of VO₂ thin films.