Abstract
Single-crystalline vanadium dioxide (VO2) nanostructures have recently attracted great attention because of their single domain metal-insulator transition (MIT) nature that differs from a bulk sample. The VO2 nanostructures can also provide new opportunities to explore, understand, and ultimately engineer MIT properties for applications of novel functional devices. Importantly, the MIT properties of the VO2 nanostructures are significantly affected by stoichiometry, doping, size effect, defects, and in particular, strain. Here, we report the effect of substrate-mediated strain on the correlative role of thermal heating and electric field on the MIT in the VO2 nanobeams by altering the strength of the substrate attachment. Our study may provide helpful information on controlling the properties of VO2 nanobeam for the device applications by changing temperature and voltage with a properly engineered strain.
Highlights
Single-crystalline vanadium dioxide (VO2) nanostructures have recently attracted great attention because of their single domain metal-insulator transition (MIT) nature that differs from a bulk sample
For the solution-dropping method, as-grown VO2 nanobeams on a r-cut sapphire were released by sonication in ethanol and the nanobeam-dispersed solution was dropped on the SiO2/Si substrate (Fig. 1a), whereas for the PDMS-transferring method, a PDMS stamp was attached and pressed onto the VO2 nanobeams grown on the r-cut sapphire substrate, followed by the detachment of the PDMS slab from the substrate
The PDMS with adhered VO2 nanobeams was strongly pressed against the transfer substrate (SiO2/Si substrate) at a moderate temperature to make a firm contact between the transfer substrate and the PDMS stamp during mechanical transfer
Summary
In this sense, we suspect that thermal hysteresis is typically due to the first-order nature of the phase transition, the extended hysteresis width can be affected by the tensile strain across the nanobeams caused by the PDMS-transferring method[17,21,38,39]. Similar to varying temperature, when altering voltage, the hysteresis width in voltage (Δ VTH) of the PDMS-transferred nanobeam device is larger than that of the solution-dropped nanobeam device Both threshold voltages (VTH↑ and VTH↓) of the former device are higher than the latter device (see Table 1 and Supplementary Figure S6 for the statistical results). These trends could be originated from the tensile strain pre-existing in this PDMS-transferred nanobeam, which is consistent
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