Polymorphism of VO2 thin film: M1, T, and M2 single phase synthesis using pulsed laser deposition

Vanadium dioxide (VO2) can undergo a reversible insulator-to-metal transition (IMT) along with a structural phase transition from monoclinic M1 to rutile tetragonal R at about 68oC, thereby making a range of optic and electronic applications possible. The structural phase transition from monoclinic M1 to rutile tetragonal R can occur via two other intermediate metastable phases of triclinic T and monoclinic M2. Due to their narrow thermodynamic stability, selective phase deposition of VO2 thin films is a major challenge. In the present study, apart from synthesizing the VO2 thin film with M1 phase, we also selectively elaborated the T and M2 phases using pulsed laser deposition (PLD) by simply controlling the repetition rate of the laser. Analysis of the struc-tural, morphological, nanomechanical, thermochromic, and optical properties of each of these polymorphs demonstrated strong dependence of these properties on the VO2 phases, and hence on the laser repetition rate. The ability to stabilize different polymorphs of VO2 thin films paves the way for novel structures that are promising for new device functionalities.