多晶六硼化镧场发射性能研究

发布时间：2018-03-30 16:33

  本文选题：场发射阴极　切入点：多晶六硼化镧(LaB6)　出处：《电子科技大学》2015年硕士论文

【摘要】：在各种高能加速器和高频微波器件等设备中,常常需要性能优良的阴极材料提供亮度高、品质好、电流密度大的电子束。与热阴极相比,场发射阴极具有不需要加热、启动快、脉冲发射电流密度大等很多优点、是电真空器件和各种高能加速器的理想电子源,近年来已成为国内外研究的热点。在各种阴极材料中,LaB6具有优异的场发射性能,但由于其熔点高、化学稳定性好,如何设计场发射阴极结构和制作成为十分关键的问题。为了提高场发射阴极的发射能力,本文设计并制备了两种结构(环状结构和梳状结构)的多晶LaB6场发射阴极,通过调整各项工艺参数,成功制作出一种电子发射性能优良的大面积多晶LaB6场发射阴极。论文主要研究内容包括:1、采用MAGIC软件模拟计算得出,改变发射体结构参数可以提高其表面场强,为后续制备工作的进行提供了理论基础。研究得出发射体结构和发射材料逸出功是影响阴极场发射能力的关键参数。逸出功越低的场发射材料,其场发射性能越好。2、采用射频磁控溅射法在基片表面沉积氮化硅保护层。研究得出随着射频功率的增加,沉积速率先增加后减小,同时沉积速率与薄膜的均匀性成反比关系。工作气压越高,薄膜沉积速率越低,而且两者成线性关系。3、采用电化学刻蚀法制备多晶LaB6场发射阴极。研究得出电解液成分、浓度、缓蚀液、水溶剂和极间电压对发射体刻蚀形貌的影响。与磷酸相比,盐酸更适合作为多晶LaB6电化学刻蚀的电解液。在电解液中,缓蚀液的比例越高,发射体表面越平整;水溶剂含量越低,发射体表面越粗糙,刻蚀速率越快。4、研究出了一种适合环状结构多晶LaB6场发射阴极的电化学刻蚀方法,其最佳制备参数为:采用光刻胶作为保护层,基底活化温度为180℃,时间为3h;电解液配比为V(HCl):V(C2H5OH):V(H2O)=1mL:20mL:20mL,极间电压为3V,电化学刻蚀时间为1h。最终成功制备出环状多晶LaB6场致发射阴极。5、自行设计搭建了测试夹具和测试装置,并对制备出的场发射阴极进行性能测试。其中,梳状结构的场发射阴极发射性能优于环状结构。梳状结构的开启电场为6~8V/μm,阈值电场为18~21V/μm。经测试,多晶材料在低真空下仍然表现出较好的稳定性与抗中毒能力,表现出LaB6作为场发射材料的优越特性。
[Abstract]:In various equipment such as high energy accelerator and high frequency microwave device, high performance cathode material is often needed to provide electron beam with high brightness, good quality and high current density. Pulse emission with high current density is an ideal electron source for electric vacuum devices and various high energy accelerators. In recent years, it has become a hot research topic at home and abroad. In all kinds of cathode materials, LaB6 has excellent field emission performance. However, due to its high melting point and good chemical stability, how to design the structure and manufacture of the field emission cathode becomes a key problem. In this paper, two kinds of polycrystalline LaB6 field emission cathodes (ring structure and comb structure) are designed and fabricated. A large area polycrystalline LaB6 field emission cathode with excellent electron emission performance has been successfully fabricated. The main research contents include: 1. The surface field strength can be improved by changing the structure parameters of the emitter by using MAGIC software. The results show that the structure of emitters and the escape work of emitters are the key parameters affecting the field emission ability of the cathode. The better the field emission property is, the better the RF magnetron sputtering method is used to deposit silicon nitride protective layer on the substrate surface. It is found that the deposition rate increases first and then decreases with the increase of RF power. At the same time, the deposition rate is inversely proportional to the homogeneity of the film. The higher the working pressure, the lower the deposition rate and the linear relationship between them. The polycrystalline LaB6 field emission cathode is prepared by electrochemical etching. The composition and concentration of electrolyte are obtained. Compared with phosphoric acid, hydrochloric acid is more suitable as electrolyte for electrochemical etching of polycrystalline LaB6. The lower the content of water solvent, the rougher the surface of emitter and the faster the etching rate. A new electrochemical etching method suitable for annular polycrystalline LaB6 field emission cathode is developed. The optimum preparation parameters are as follows: photoresist is used as protective layer. The substrate activation temperature is 180 鈩，

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