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Spindt型场发射阴极,在初期老炼过程中容易失效,其表现为发射尖锥和栅极间短路、漏电,或是真空电弧损伤。引起Spindt阴极失效的一个主要原因,分析认为是存在于发射尖锥表面、栅极边缘以及承载尖锥的二氧化硅空腔中的金属颗粒附着。这些金属颗粒,产生于双向沉积制作发射尖锥过程中,它们在牺牲层剥离时脱落,并且没有在随后的纯水清洗过程中得到有效去除。这些金属颗粒的存在,即便没有导致初期阴极失效,也可能成为阴极大电流应用,如微波真空功率器件应用的潜在障碍。研究中提出了在常规清洗工艺中引入超声波清洗和兆声波清洗,初步试验研究表明,振动频率28 k Hz的超声波清洗,容易造成阴极损伤,并且对微小颗粒的去除效果不好,而频率1 MHz的兆声波清洗,则可近似无损地将阴极失效率大幅降低。
Spindt-type field emission cathode, easy to fail during the initial aging process, which is characterized by a short circuit between the emitter tip and the gate, leakage, or vacuum arc damage. One of the main causes of failure of the Spindt cathode is the analysis of the attachment of metal particles present in the launch cone surface, the gate edge, and the silica-carrying cavity carrying the cone. These metal particles, which arise during the bidirectional deposition of the launch cone, break off when the sacrificial layer is peeled off and are not effectively removed during subsequent clean water purging. The presence of these metal particles, if not causing initial cathode failure, can also be a potential barrier to high cathode current applications such as microwave vacuum power device applications. In the study, ultrasonic cleaning and megasonic cleaning were introduced into the conventional cleaning process. Preliminary experimental studies have shown that ultrasonic cleaning with a vibration frequency of 28 kHz easily causes cathode damage and has a poor effect on removing fine particles. However, the frequency of 1 MHz Megasonic cleaning, the failure rate of the cathode can be substantially reduced without loss.