In situ Raman-scattering mapping and resistance study of the VO2 metal-insulator phase transition

Abstract

In this study, a large-area single-phase VO2 film was successfully prepared on a Si (100) substrate by reactive magnetron sputtering deposition. The thickness of the VO2 film is approximately 220 nm. The phase transition temperature is about 67 °C, with more than three orders of magnitude of the resistance change. X-ray diffraction patterns obtained at different temperatures indicate the coexistence of two phases during the VO2 phase transition process, where a portion of the grains first transform from a monoclinic structure to a rutile structure, and then phase transition expands throughout the film. In situ Raman-scattering mapping scans further prove that the monoclinic-to-rutile phase transition occurs gradually in polycrystalline VO2 films, in which monoclinic and rutile phases coexist from 55 °C to 80 °C. Electrical resistance of the film will change dramatically when the volume fraction of monoclinic phase decreases to 43.5%, or the volume fraction of rutile phase increases to 55.5%. The phase transition temperature differs among the grains in the polycrystalline VO2 film. This study provides an important scientific approach for elucidating the mechanism of the metal-insulator phase transition.