Ultrafast, Kinetically Limited, Ambient Synthesis of Vanadium Dioxides through Laser Direct Writing on Ultrathin Chalcogenide Matrix.

Vanadium dioxide (VO) is a strongly correlated electronic material and has attracted significant attention due to its metal-to-insulator transition and diverse smart applications. Traditional synthesis of VO usually requires minutes or hours of global heating and low oxygen partial pressure to achieve thermodynamic control of the valence state. Further patterning of VO through a series of lithography and etching processes may inevitably change its surface valence, which poses a great challenge for the assembly of micro- and nanoscale VO-based heterojunction devices. Herein, we report an ultrafast method to simultaneously synthesize and pattern VO on the time scale of seconds under ambient conditions through laser direct writing on a VS "canvas". The successful ambient synthesis of VO is attributed to the ultrafast local heating and cooling process, resulting in controlled freezing of the intermediate oxidation phase during the relatively long kinetic reaction. A Mott memristor based on a VS-VO-VS lateral heterostructure can be fabricated and integrated with a MoS channel, delivering a transistor with abrupt switching transfer characteristics. The other device with a VSO channel exhibits a large negative temperature coefficient of approximately 4.5%/K, which is highly desirable for microbolometers. The proposed approach enables fast and efficient integration of VO-based heterojunction devices and is applicable to other intriguing intermediate phases of oxides.