3D Local Manipulation of the Metal–Insulator Transition Behavior in VO₂ Thin Film by Defect-Induced Lattice Engineering

The ability to manipulate the metal–insulator transition (MIT) of metal oxides is of critical importance for fundamental investigations of electron correlations and practical implementations of power efficient tunable electrical and optical devices. Most of the existing techniques including chemical doping and epitaxial strain modification can only modify the global transition temperature, while the capability to locally manipulate MIT is still lacking for developing highly integrated functional devices. Here, lattice engineering induced by the energetic noble gas ion allowing a 3D local manipulation of the MIT in VO₂ films is demonstrated and a spatial resolution laterally within the micrometer scale is reached. Ion-induced open volume defects efficiently modify the lattice constants of VO₂ and consequently reduce the MIT temperature continuously from 341 to 275 K. According to a density functional theory calculation, the effect of lattice constant variation reduces the phase change energy barrier and therefore triggers the MIT at a much lower temperature. VO₂ films with multiple transitions in both in-plane and out-of-plane dimensions can be achieved by implantation through a shadow mask or multienergy implantation. Based on this method, temperature-controlled VO₂ metasurface structure is demonstrated by tuning only locally the MIT behavior on the VO₂ surfaces.