Defining Laser-Induced Phase Transition and Thermal Response of VO₂ by Raman Spectroscopy: A Comparative Study of...

Vanadium dioxide (VO₂) is a strongly correlated transition metal oxide that undergoes a reversible metal-insulator transition (MIT) accompanied by a structural phase transformation, making it highly sensitive to localized thermal excitation. The effect of Raman laser irradiation on the phase stability and oxidation behavior of VO₂ materials fabricated via different methods is systematically investigated. VO₂ powder prepared by Rapid Thermal Annealing (RTA) and three VO₂ -based thin films deposited on Al₂O₃ substrates (VO₂/PVP composite, sol-gel, and Reactive Biased Target Ion Beam Deposition (RBTIBD)) were characterized by X-ray diffraction (XRD), along with field-emission scanning electron microscopy (FE-SEM), UV-Vis-IR spectroscopy, temperature-dependent measurements to determine their thermochromic transition behavior, while Raman spectroscopy under controlled laser excitation was employed as a localized heating source to probe thermal response and phase stability. Under 638 nm excitation, VO₂ powder rapidly oxidized to higher vanadium oxides at intermediate laser power, whereas the VO₂/PVP thin film exhibited delayed oxidation, requiring higher power for complete transformation. In contrast, sol-gel and RBTIBD thin films analyzed using 532 nm excitation did not undergo oxidation but instead showed a fully reversible laser-induced phase transition between monoclinic VO₂ (M) and rutile VO₂ (R). This work establishes a clear correlation between fabrication method, microstructure, and laser-induced phase stability in VO₂ materials.