External strain dependent optical studies of VO₂ thin films

Hsiao-Wen Chen^1*, C. I. Li (李建毅)², C. H. Ma (馬俊皓)², Y. H. Chu (朱英豪)², H. L. Liu(劉祥麟)¹

¹Department of Physics,, National Taiwan Normal University, Taipei, Taiwan
²Department of Materials Science Engineering, National Chiao Tung University, Hsinchu, Taiwan

* Presenter:Hsiao-Wen Chen, email:josephmdtw@gmail.com

We present the stain dependent Raman scattering and optical transmittance measurements of VO₂ thin films. The VO₂ thin films were grown on muscovite substrate by using pulsed laser deposition and molecular-beam epitaxy. By applying an external compressive strain, the observed B_g and A_g symmetry Raman phonon modes at approximately 438 and 616 cm^-1 exhibit a buleshift. Upon passing through the metal-insulator transition (MIT) temperature at about 62 °C, the tensile strain optical transmittance spectra show the MIT temperature shifts to higher temperature. By contrast, the compressive strain dependent optical transmittance spectra show the MIT temperature shifts to lower temperature. The ratio of MIT temperature shift to stain is 3.7 °C/%. This phenomenon was associated with the external strain obstructs the structural phase transition of VO₂ thin films.

Keywords: VO₂, raman spectra, strain, transmittance spectra