Enhanced metal-insulator transition in freestanding VO2 down to 5 nm thickness

TL;DR

This study demonstrates a significantly enhanced metal-insulator transition in ultrathin freestanding VO2 membranes down to 5 nm, achieved through membrane transfer and buffer layer insertion, promising for flexible electronic applications.

Contribution

It reports the first observation of enhanced MIT in freestanding VO2 membranes as thin as 5 nm, surpassing previous limitations in ultrathin film MIT performance.

Findings

MIT enhancement over 400% at 5 nm thickness

Successful transfer of large-scale freestanding membranes

Potential for integration into flexible electronics

Abstract

Ultrathin freestanding membranes with a pronounced metal-insulator transition (MIT) provides huge potential in future flexible electronic applications as well as a unique aspect of the study of lattice-electron interplay. However, the reduction of the thickness to an ultrathin region (a few nm) is typically detrimental to the MIT in epitaxial films, and even catastrophic for their freestanding form. Here, we report an enhanced MIT in VO2-based freestanding membranes, with a lateral size up to millimetres and VO2 thickness down to 5 nm. The VO2-membranes were detached by dissolving a Sr3Al2O6 sacrificial layer between the VO2 thin film and c-Al2O3(0001) substrate, allowing a transfer onto arbitrary surfaces. Furthermore, the MIT in the VO2-membrane was greatly enhanced by inserting an intermediate Al2O3 buffer layer. In comparison to the best available ultrathin VO2-membranes, the enhancement of MIT is over 400% at 5 nm VO2 thickness and more than one order of magnitude for VO2 above 10 nm. Our study widens the spectrum of functionality in ultrathin and large-scale membranes, and enables the potential integration of MIT into flexible electronics and photonics.