Synthesis Of High-quality VO₂ Thin Film And Its Application In Devices

Transition metal oxides?TMOs?are a fascinating class of materials due to their wide ranging electronic,optical,and magnetic properties.VO₂ has been extensively studied as a model system for metal-insulator transition?MIT?,ever since its phase-switching behavior at close to room temperature was discovered.Most of these remarkable properties originate from interplay between the lattice and orbital degrees of freedom of the material.VO₂ films constitute a new functional material,showing a reversible transition between a low-temperature semiconductor phase and a high-temperature metal phase at about 68°C.High-quality VO₂ films have been successfully synthesized on SiO₂/Si substrates by a simple and efficient method in a tube furnace.The as-synthesized VO₂ films were structurally uniform and single-crystalline.These films show a large resistance change of more than four orders of magnitude with a 5 K width of the hysteresis loop as the temperature is cycled through the phase transition.VO₂ thin-film devices have been fabricated by Inductive Coupled Plasma etching?ICP?and deposition processes.The current response of devices under light ilumination and bias exhibited a higher sensitivity and a much wider pressure range than that without light ilumination.Experimental data also revealed that the current response of a VO₂ film device shows an approximately linear dependence on the logarithm of air pressure.These high-quality VO₂ thin films with excelent properties have potentially promising application in vacuum sensor.On the other hand,we fabricated vanadium oxide?VO₂?metal-oxide-semiconductor field-effect transistors?MOSFETs?device to describe a prototype of a field effect transistor based on the Mott metal-insulator transition?MIT?in single-crystal VO₂ thin film.We present a detailed account of our experimental investigation into three-terminal field effect transistor-like devices using thin film VO₂ as the channel layer.It has been shown that the modulation of the channel resistance and the thickness of inversion layer can be achieved by change temperature and gate voltage?V_g?of the device.The phase transition temperature can be turned from 342 K in the bulk VO₂ to as low as 318 K by changing the gate voltage of VO₂ film device.The photoresponse properties of VO₂-film based on FET have been studied.Photoelectrical results indicate that the as-prepared VO₂-film FET have an excellent sensitivity and a good reproducibility as a photodetector.