VO2 Nanocrystals Array for Low-Power Resistive Switches

At the moment, new concepts of memory and neuromorphic computing devices are developing rapidly based on the semiconductor-metal phase transition effect in some metal oxides, such as vanadium dioxide $\left(\mathrm{VO}_{2}\right)$. The resistive switching in VO
2
can be achieved by applying a voltage or current that induces Joule heating in the device and triggers the semiconductor-metal transition. However, the structural phase transition in VO
2
, accompanied by a sharp change in the lattice constant, seriously limits the use of polycrystalline films in switching devices. This paper reports on the fabrication of low-power vertical two-contact resistive switches based on disordered array of high-quality VO
2
nanocrystals. Unlike a polycrystalline film, an array of single nanocrystals can reduce the threshold switching power by three orders of magnitude and achieve a high stability and durability due to the small contact area of the nanocrystals with the substrate. Minimal values of threshold voltage of 0.4 V and threshold power of 13 $\mu \mathrm{W}$ were reached. The proposed design of switches combines formation simplicity, comparable to polycrystalline films based switches, and significantly reduces the threshold power. Our fabrication approach of energy-efficient devices can be applied for a number of new semiconductor-metal phase transition based applications for nanoelectronics and nanophotonics.