石墨烯冷阴极大电流场发射损伤机制的微观原位研究

发展高性能真空电子器件要求具有发射大电流和高电流密度的冷阴极材料。冷阴极材料的电子发射能力是制约真空电子器件性能的关键因素。现阶段，大电流冷阴极材料的性能和稳定性是制约真空电子器件发展的瓶颈。石墨烯由于具有原子级别的发射尖端，优异的导电导热能力和二维散热平面，是具有较大潜力的大电流场发射材料。本项目将重点研究大电流发射过程中石墨烯的发射稳定性和大电流损伤机制。拟采用透射电子显微镜表征技术结合原位场发射纳米探针的测试技术，从原子尺度观察和研究石墨烯材料的结构和形貌在强电场大电流发射环境下的变化情况。其中，重点讨论石墨烯在强场导致的结构拉伸与焦耳热导致的断裂的两种损伤机制，判定出现不同损伤机制的临界条件，建立二维原子晶体材料石墨烯损伤机制的模型，为实现高性能高稳定性的石墨烯大电流冷阴极提供理论指导和可行性保证。

Cold cathode material with high current and current density is essential for high performance vacuum electronic device. The poor character in high current and stability of cold cathode material hampers the development of vacuum electronic device. Graphene has atomic sharp emitting edge and 2D plane area, excellent electric and thermal conductivity, and is considered as a kind of high current field emission material. In this project, we focus on the high current field emission characterization and the related breakdown mechanism of graphene cold cathode. We will combined the HRTEM characterization with the field emission nano-probe techniques to in-situ investigate the structure and morphology development of graphene during the high current field emission in nano scale. We will discuss two breakdown mechanisms which origins from high electric field stretching and Joule heating, clarify the critical condition for each breakdown mechanism and create the breakdown model of graphene during field emission. This work would provide a way to understand the breakdown phenomena in a direct view and demonstrate the possibility to realize a high performance field emission cold cathode.