Wafer-Scale Transfer and Integration of Tungsten-Doped Vanadium Dioxide Films.

Modern optoelectronic devices trend toward greater flexibility, wearability, and multifunctionality, demanding higher standards for fabrication and operation temperatures. Vanadium dioxide (VO), with its metal-insulator transition (MIT) at 68 °C, serves as a crucial functional layer in many optoelectronic devices. However, VO usually needs to grow at >450 °C in an oxygen-containing atmosphere and to function across its MIT temperature, leading to low compatibility with most optoelectronic devices, especially on flexible substrates. In this work, we report a layer-by-layer transfer method of wafer-scale tungsten-doped VO films, which enables sequential integration of the VO films with low MIT temperatures (down to 40 °C) onto arbitrary substrates. Notably, by stacking multiple VO films with different doped levels, a quasi-gradient-doped VO architecture can be achieved, effectively broadening the MIT temperature window and reducing the hysteresis of VO. These integrated VO films find a wide scope of applications in flexible temperature indicator strips, infrared camouflage devices, nonreciprocal ultrafast light modulators, and smart photoactuators. Our work promotes the development of more flexible and tunable optoelectronic devices integrated with VO.