Key Laboratory of Polar Materials and Devices (Ministry of Education of China), Department of Electronic Engineering, East China Normal University, Shanghai 200241, China.
ACS Appl Mater Interfaces. 2011 Jun;3(6):2057-62. doi: 10.1021/am200291a. Epub 2011 Jun 2.
Bundlelike VO(2)(B) nanostructures were synthesized via a hydrothermal method, and VO(2)(M(1)/R) nanobundles were obtained after a heat-treatment process. Structural characterization shows that these nanobundles are self-assembled by VO(2) nanowires, and VO(2)(M(1)/R) nanobundles have better crystallinity. Temperature-dependent field-emission (FE) measurement indicates that FE properties of these two phases of nanobundles can both be improved by increasing the ambient temperature. Moreover, for the VO(2)(M(1)/R) nanobundles, their FE properties are also strongly dependent on the temperature-induced metal-insulator transitions process. Compared with poor FE properties found in the insulating phase, FE properties were significantly improved by increasing the temperature, and about a three-orders-of-magnitude increasing of the emission current density has been observed at a fixed field of 6 V/μm. Work function measurement and density-functional theory calculations indicated that the decrease of work function with temperature is the main reason that caused the improvement of FE properties. These characteristics make VO(2)(M(1)/R) a candidate material for application of new type of temperature-controlled field emitters, whose emission density can be adjusted by ambient temperature.
通过水热法合成了类似束状的 VO(2)(B) 纳米结构，经过热处理过程得到了 VO(2)(M(1)/R)纳米束。结构表征表明，这些纳米束是由 VO(2)纳米线自组装而成的，并且 VO(2)(M(1)/R)纳米束具有更好的结晶度。温度依赖的场发射（FE）测量表明，通过提高环境温度可以改善这两种纳米束的 FE 性能。此外，对于 VO(2)(M(1)/R)纳米束，其 FE 性能也强烈依赖于温度诱导的金属-绝缘体转变过程。与绝缘相中较差的 FE 性能相比，通过增加温度可以显著提高 FE 性能，并且在固定的 6 V/μm 电场下，发射电流密度已经观察到约三个数量级的增加。功函数测量和密度泛函理论计算表明，功函数随温度的降低是导致 FE 性能提高的主要原因。这些特性使得 VO(2)(M(1)/R)成为新型温度控制场发射体的候选材料，其发射密度可以通过环境温度进行调节。
