电场诱导二氧化钒绝缘-金属相变的研究进展

二氧化钒(VO_2)是电子强关联体系的典型代表,其晶体结构在特定阈值的温度、电场、光照和压力等物理场作用下会发生由单斜金红石结构向四方金红石结构的可逆转变,从而引发绝缘-金属相变.其中,电场诱导VO_2绝缘-金属相变后的电导率可提高2-5个数量级,在可重构缝隙天线、太赫兹辐射以及智能电磁防护材料等领域具有广阔的应用前景,成为近年来人们的研究热点.首先,简要概述了VO_2发生绝缘-金属相变时晶体结构和能带结构的变化,进而从电场诱导VO_2绝缘-金属相变的研究方法、响应时间、临界阈值场强调控以及相变机理几个方面系统总结和评述了近年来国内外学者在该领域的重要发现和研究进展.最后,指出了当前VO_2绝缘-金属相变研究存在的问题,并展望了未来的发展方向.

Research progress of metal-insulator phase transition in VO2 induced by electric field

Vanadium dioxide (VO₂) is a typical representative of strongly correlated electronic systems, which undergoes a reversible transition from the insulator phase to metal phase, induced by a certain threshold for each of temperature, electric field, illumination and pressure. The crystal structure of VO₂ will undergo a reversible transition from monoclinic structure to tetragonal rutile structure when the phase transition happens, which is considered as the microscopic mechanism of VO₂ metal-insulator transition (MIT). The conductivity of VO₂ can be increased by 2-5 orders of magnitude when the MIT is induced by electric field, which makes VO₂ possess good application prospects in the fields of restructurable slot antenna, terahertz radiation, intelligent electromagnetic protection materials, etc. Therefore, the reversible metal-insulator phase transition in VO₂, induced by electric field, has long been a research hotspot, which however, has been seldom reported. Firstly, in this paper, the changes of the crystal structure and energy band structure of VO₂ during MIT are introduced briefly. The methods of regulating the phase transition are given, including temperature control, bandwidth and band-filling control. Then, the important discovery and research progress of VO₂ MIT induced by electric field based on the research method, response time, critical threshold field and phase transition mechanism are summarized and reviewed comprehensively. The method of studying the VO₂ phase transition relates to its structure, including planar structure, three-terminal gated?eld effect switch and sandwiched layer structure. The sandwich layer structure is more suitable for investigating the MIT characteristics of VO₂ in experimental stage because of its structural advantage of preparation and test. The response time of VO₂ MIT can be completed in nanoseconds, of which the substantial parameter has been revealed by many reports, also including the excellent reversibility of VO₂ MIT. The MIT critical threshold field of the VO₂ film can be tuned by element doping, coexistence of multivalent vanadium oxides and multiple physical field synergism effectively. The MIT mechanism of VO₂ induced by electric field has been proposed so far, which includes joule heating mechanism and pure electric field mechanism, and the latter is considered to be more likely to give a reasonable explanation. Finally, in the paper the current problems of the VO₂ MIT research and the near-future development direction of the VO₂ MIT materials are also pointed out.