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Description
Vanadium dioxide (VO2) is a material which has a special characteristic that can change its properties drastically called metal-Insulator transition (MIT). The MIT of VO2 occurs at temperature about 68๐C under atmospheric pressure which change its phase from monoclinic to rutile phase, result in their different properties and structure. This characteristic of VO2 can be used for application such as smart windows[1]. Moreover, some material can be used to improve VO2 film quality. In this work, bilayer-graphene were deposited on top of VO2/Al2O3 of 50 nm and 100 nm VO2 and were studied via temperature-dependent Raman spectroscopy technique. The results from Raman spectrum indicate that the lattice parameter mismatch between bilayer-graphene and VO2 induce compressive strain on graphene and in-plane tensile strain on VO2 according to the observed blue shift of VO2 Raman modes. From the temperature-dependent Raman results, the monoclinic VO2 Raman peaks diminished as temperature reach 60-65°C while the TMIT measured by temperature dependent resistance of bare VO2 is equal to 70°C. Moreover, an unexpected behavior from graphene can be observed in graphene/VO2. For graphene/SiO2 G-peak position tends to red shift as temperature increase[3]. However, the G-peak position observed from graphene/VO2 structure begins with red shift and turn to blue shift at ~60°C instead of only red shift.
References
[1] Y. Cui, Y. Ke, C. Liu, Z. Chen, et al. Thermochromic VO2 for Energy-Efficient Smart Windows. Joule, Volume 2, Issue 9-2018, 1707-1746. https://doi.org/10.1016/j.joule.2018.06.018
[2] Zhou, H., Li, J., Xin, Y., Cao, X., Baoa, S., and Jin, P. (2015). Enhanced optical response of hybridized VO2/graphene films. J. Mater. Chem. C, 3(19), 5089-5097. doi:10.1039/C5TC00448A
[3] Wang, W., Peng, Q., Dai, Y. et al. Temperature dependence of Raman spectra of graphene on copper foil substrate. J Mater Sci: Mater Electron 27, 3888–3893 (2016). https://doi.org/10.1007/s10854-015-4238-y
