金属基底对石墨烯薄膜阴极气体击穿稳定性影响

利用石墨烯二维材料极好的场发射能力和发射稳定性,提出了石墨烯阴极提高气体开关击穿稳定性的技术路线。采用化学气相沉积法和基底腐蚀转移法两种方法制备金属基底石墨烯薄膜阴极。利用扫描电子显微镜和拉曼光谱表征了石墨烯薄膜阴极质量,确认了石墨烯层数和均匀性。实验研究了两种石墨烯薄膜阴极气体开关,在微秒脉冲均匀电场作用下的击穿特性,获得了击穿电压幅值和分散性的变化规律。结果表明:当气体为0.6 MPa N2、电极间距为5 mm时,铜基底石墨烯薄膜阴极平均击穿电压为85.9 kV,相对标准差为3.2%;不锈钢基底石墨烯薄膜阴极平均击穿电压仅为59.8 kV,相对标准差为2.4%。当两种阴极击穿电压均为80 kV时,相对标准差比较,不锈钢基底仅为铜基底的44%。分析认为,不锈钢基底石墨烯薄膜质量优于铜基底,石墨烯薄膜导致阴极表面微观场增强因子更高,表面分布更均匀,在电场作用下场致发射产生均匀稳定的大量初始电子流,降低了气体开关击穿电压,有效提高了击穿稳定性。

Influence of metal matrix materials on self-breakdown stability of graphene film cathode

Graphene has attracted great interest for its distinctive band structure and physical properties.Results from previous studies show that a graphene cathode can provide stable field emission and intense emission in vacuum.This paper presents two metal matrix graphene film cathodes prepared by different methods.One is a copper/graphene matrix cathode grown by chemical vapor deposition,the other is a stainless steel/graphene matrix cathode transferred by substrate corrosion.The surface morphology of the graphene films on these two cathodes was examined using a scanning electron microscope(SEM)and Raman spectroscopy.The thickness and uniformity of the graphene film was evaluated.Gas spark switches based on these two cathodes were developed.The impulse-breakdown characteristics of these switches in a quasi-uniform electric field were studied.When the gap length is 5 mm and the gas pressure is 0.6 MPa,the average breakdown voltage(UBD)for copper/graphene matrix cathode is nearly 85.9 kV,and the voltage jitter is 3.2%;the average UBD for stainless steel/graphene matrix cathode is nearly 59.8 kV,and the voltage jitter is 2.4%.According to preliminary analysis,the surface state of the cathode and the quality of the graphene film directly affect the breakdown stability of the gas switch.