Stabilization of the VO 2 (M2) Phase and Change in Lattice Parameters at the Phase Transition Temperature of W X V 1- X O 2 Thin Films.

Various methods have been used to fabricate vanadium dioxide (VO 2 ) thin films exhibiting polymorph phases and an identical chemical formula suited to different applications. Most fabrication techniques require post-annealing to convert the amorphous VO 2 thin film into the VO 2 (M1) phase. In this study, we provide a temperature-dependent XRD analysis that confirms the change in lattice parameters responsible for the metal-to-insulator transition as the structure undergoes a monoclinic to the tetragonal phase transition. In our study, we deposited VO 2 and W-doped VO 2 thin films onto silica substrates using a high repetition rate (10 kHz) fs-PLD deposition without post-annealing. The XRD patterns measured at room temperature revealed stabilization of the monoclinic M2 phase by W 6+ doping VO 2 . We developed an alternative approach to determine the phase transition temperatures using temperature-dependent X-ray diffraction measurements to evaluate the a and b lattice parameters for the monoclinic and rutile phases. The a and b lattice parameters versus temperature revealed phase transition temperature reduction from ∼66 to 38 °C when the W 6+ concentration increases. This study provides a novel unorthodox technique to characterize and evaluate the structural phase transitions seen on VO 2 thin films.