Research On Fabrication And Electrical Property Of Vanadium Dioxide Nanowires

Vanadium dioxide?VO₂?has recently attracted great attention because of its typical metal-insulator transition.VO₂ displays a transition from monoclinic phase to rutile-type phase when heated it to its critical temperature of 68 °C,accompanying great change in electrical resistance,optical transmittance,mechanical and magnetic property.Based on this excellent characteristics,VO₂ can be developed as some interesting application.Nowadays,electronic devices are developing in the direction toward miniaturization,so low-dimension nanomaterial is attracting more and more attention and research.Research has shown that VO₂ nanowire due to its single crystalline shows obvious metal-insulator transition,which need to be further explored.For these reasons,high quality VO₂ nanowires were fabricated by chemical vapor deposition and pulse laser deposition.Using thermo-electrical testing platform,the electrical property of VO₂ nanowires were studied in detail,which provides experimental base for future application.High quality VO₂ nanowires were successfully grown by chemical vapor deposition,and the effect of substrates on nanowires growth had been clarified.It was found that substrate surface influences the growth of nanowires a lot.The greatest nanowires density was achieved on rough surface of quartz substrate,while polished quartz and other species of substrates yielded much lower densities of nanowires that were embedded in the substrates.Orientation-controlled nanowires were grown by using c-cut sapphire substrates.In order to obtain higher density nanowires,we attempted to exploit the growth process of VO₂ nanowires by pulsed laser deposition.The optimum technique for preparation VO₂ nanowires is showing in the following condition: substrate temperature 750 °C,Oxygen pressure 5 Pa,laser frequency 1 Hz,pulse count 3000.Likewise,the growth orientation of nanowires was also influenced by crystal structure of substrate.Finally,the electrical property of single VO₂ nanowires was investigated.It was found that single crystal VO₂ nanowires shows excellent metal-insulator transition,and the nanowires with mismatch-induced strain have higher phase transition temperature and wider width of hysteresis than free-standing nanowires.The metal-insulator transition of VO₂ nanowires was achieved by applying a voltage of several volts,and the phase transition voltage decreased linearly with increasing temperature.Similar to varying temperature,vanadium dioxide nanowires also displayed higher phase transition voltage owing to substrate-induced strain.Moreover,the metal-insulator transition of vanadium dioxide kept stable when applying a cyclic sweep voltage,which can be potentially used as resistive switching or flash memory.