Phase Transitions in Vanadium Dioxide Thin Film Heterostructures Studied by Raman Spectroscopy
Studying phase transitions in materials is essential for condensed matter physics, as transitions between different crystal structures can influence the properties of a material drastically. Raman spectroscopy is one of several experimental techniques used to study crystallographic phases and phase transitions, since Raman spectra are sensitive to subtle transformations of crystal structures. In this study, Raman spectroscopy was applied for the investigation of thin film heterostructures of vanadium dioxide, VO2, epitaxially grown on TiO2 (001) substrates. Ultraviolet excitation (363.8 nm) was used in order to minimize the substrate signal. Spectra measured in the temperature range 250 – 300 K revealed a structural phase transition from a monoclinic phase to a tetragonal phase, followed by electronic insulator-metal transition, in the temperature range 275 – 285 K. These transitions are determined from the temperature evolution of Raman intensities of vibrational modes specific to the monoclinic structure of the material. The transition temperatures differ between heating and cooling: upon cooling the transition occurs at lower temperatures than when heating, thus showing some temperature hysteresis.
Spinuzzi, Joseph, "Phase Transitions in Vanadium Dioxide Thin Film Heterostructures Studied by Raman Spectroscopy" (2017). 2017 Undergraduate Research and Scholarship Conference.