  Controlling the strain induced poly-domains and phase transition in
correlated oxide material are important for high performance devices
fabrication. Though the electronic transport in the strained oxide film at
macroscopic scales can be directly measured, the anisotropic electronic state
and the controllable phase separation cross the insulator-to-metal transition
within nanoscale size are still elusive. Here, we selected VO2 crystal film as
a prototypical oxide and achieved the anisotropy electronic phase separation
via injecting nanoscale-size Helium ions flux into VO2 film at room
temperature. More importantly, this nanoscale phase separation was directly
visualized by infrared near-field imaging measurements, showing the pronounced
and unique cR-axis dependent anisotropy. Our results offered new insights
towards understanding the anisotropic nanoscale phase separation in strained
metal oxide films.
