多维复合纳米材料的超强场致发射及器件的研究

If the field-emission cathode is applied in the power electronic device, it can give high output power, very fast responding time and high frequency which are the same as the vacauume electronic devices. Apart from these, the dimension of device can be miniaturized. Therefore, the development of high power field-emission electronic devices is very important for the national security and defense. In the high power electronic device, the key issues are high electron-emission current and large current density. In principle, the field-emission electron source should provide the better performance than that of the thermal-emission electron source. However, according to the results reported by references, the total field-emission current and average current density are much smaller than that of thermal-emission electron source when the emission area is a few square milimeters. At this moment, if the field-emission current is increased further, field emitters will be destoryed and the current will degrade quite fast. In this project, the mechansim of ultra-high field emission will be investigated, and the compounded nano structures will be design and synthesised to enhance the field-emission performance.The pattern and structure of field emitters array will be also optimized to decrease the screen effect and bringe effect. Thus, the emission uniformity will be improved. Finally, the field-emission current and current density which are larger than that of the thermal-emission will be obtained.Both the theortical results and experimental results obatined in this project can support the application of field-emission electron source in the high power electronic devices.

采用场致发射冷阴极的功率电子器件既保留了真空器件大功率、快速响应和高频率等优点，又可以实现微型化和集成化，因此其发展对我国的国防和国家安全具有重要意义。在这些功率器件中，大电流和高密度电子发射是需要攻克的核心问题。理论上场致发射可以获得比热电子发射更好的电流和电流密度。但是从已经公开报道的研究结果可以看出，当发射面积非常小时，场致发射电流密度可以远高于热电子发射；当发射面积较大时，如数平方毫米，大电流的场致发射导致发射体的损毁和电流的急剧跌落。 本项目将在前期工作基础上，研究基于纳米材料的超强场致发射（总电流和平均电流密度均大于普通的热电子发射）机制，探索多维复合纳米场致发射材料，提出新的场致发射阵列结构，获得优于热电子发射的场发射电流和电流密度，为场致发射电子源在功率电子器件中的应用奠定基础。

本项目针对大电流场致发射机制、新型发射材料和器件应用这一研究目标，从理论分析和计算、场发射材料制备和表征、场发射器件制备和性能测试等方面对碳纳米管/石墨烯等场致发射体进行了深入的研究。我们重点研究了大电流发射情况下，热效应对场致发射的影响，提出了热助气体分子脱附和高温下Schottky 发射两种影响电子电流的工作模型，并对该模型进行了理论分析和实验验证；本项目深入研究了低熔点Bi/碳纳米管复合场发射体的结构特征和制备工艺，最后获得了达到任务书要求的电子发射能力；本项目还研究了悬浮石墨烯、BaO纳米线等纳米结构的场发射性能和电子运动状态。最后本项目尝试将我们所研制的场发射电子源应用于快速成像X射线管、FEL微波电子枪以及柔性发光器件，实验结果证明本项目研制的场发射阴极在功率电子器件的潜在应用价值。. 本项目研制的场发射阴极发射电流可以大于50mA，电流密度大于4A/cm2，5小时发射电流跌落小于10%。通过本项目研究，我们申请发明专利12项，授权3项，在国际刊物上发表SCI收录论文23篇（已标注），在国际会议上做邀请报告3次。本项目已经完成项目任务书的预定研究内容，达到预期技术指标和成果要求。