Wafer-scale freestanding vanadium dioxide film

Vanadium dioxide (VO2), with well-known metal-to-insulator phase transition, has been used to realize intriguing smart functions in photodetectors, modulators, and actuators. Wafer- scale freestanding VO2 (f-VO2) films are desirable for integrating VO2 with other materials into multifunctional devices. Unfortunately, their preparation has yet to be achieved because the wafer-scale etching needs ultralong time and damages amphoteric VO2 whether in acid or alkaline etchants. Here, we achieved wafer-scale f-VO2 films by a nano-pinhole permeation-etching strategy in 6 min, far less than that by side etching (thousands of minutes). The f-VO2 films retain their pristine metal-to-insulator transition and intrinsic mechanical properties and can be conformably transferred to arbitrary substrates. Integration of f-VO2 films into diverse large-scale smart devices, including terahertz modulators, camouflageable photoactuators, and temperature-indicating strips, shows advantages in low insertion loss, fast response, and low triggering power. These f-VO2 films find more intriguing applications by heterogeneous integration with other functional materials.

Automated summary

By using a nano-pinhole permeation-etching strategy, wafer-scale freestanding VO2 films have been successfully prepared within 6 minutes, showing advantages in integration with other materials and retaining their metal-to-insulator transition and mechanical properties. These films can be conformably transferred to arbitrary substrates and integrated into diverse large-scale smart devices with low insertion loss, fast response, and low triggering power.