Substrate Effect on Optical Properties of Insulator-Metal Transition in VO2 Thin Films

TL;DR

This study examines how different substrates affect the phase transition temperature and optical Raman spectra of VO2 thin films, revealing substrate-dependent transition temperatures and optimal Raman measurement conditions.

Contribution

It provides new insights into substrate influence on VO2 phase transition temperature and Raman spectral characteristics, aiding in better material characterization.

Findings

VO2 on quartz transitions at 50°C, on sapphire at 68°C

Longer wavelength laser yields clearer Raman spectra

No polarization dependence observed in Raman signals

Abstract

In this paper we used Raman spectroscopy to investigate the optical properties of vanadium dioxide (VO2) thin films during the thermally induced insulating to metallic phase transition. We observed a significant difference in transition temperature in similar VO2 films grown on quartz and sapphire substrates: the film grown on quartz displayed the phase transition at a lower temperature (Tc=50C) compared a film grown on sapphire (Tc=68C). We also investigated differences in the detected Raman signal for different wavelengths and polarizations of the excitation laser. We found that for either substrate, a longer wavelength (in our case 785 nm) yielded the clearest VO2 Raman spectra, with no polarization dependence.