Fabrication of VO2 Hierarchical Micro-Nanostructure Arrays by Oxidation Scanning Probe Lithography

Vanadium dioxide is one of the most promising materials for nanoelectronics and photonics devices. However, the phase transition causes a change in the lattice constant, leading to significant mechanical stresses that contribute to the rapid degradation of electronic devices based on polycrystalline films. To address this issue, nanoscale VO
2
single crystals and nanostructures can be utilized. However, current nanostructuring methods have a significant drawback due to the use of aggressive chemical environments and the difficulty in controlling the formation of nanostructures. In this study, we have developed a technique for the formation of hierarchical nanostructures of amorphous VO
2
using the raster oxidation scanning probe lithography method. The study investigated the conditions for the oxidation process of an amorphous VO
2
film to V
2
O
5
and the removal of V
2
O
5
nanostructures in water. It has been demonstrated that the controlled reduction in the size of the array elements can be achieved by repeatedly removing the forming native oxide, V
2
O
5
, in water. Furthermore, the residual layer of VO
2
film on the silicon substrate may also be removed through this method, thus forming arrays of free-standing VO
2
nanoislands. The proposed technique is promising for metasurface and tunable photonic crystal fabrication.