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Highly thermo-stable nano electron sources for various field emission applications

Summary form only given. Field emission (FE) devices based on sharp cold cathodes such as carbon nanotubes (CNTs) have long been a hot issued research subject for advanced vacuum device applications. Especially, the utilization of these cathodes is an attractive alternative for the replacement of thermionic cathodes for generating X-rays. Generally, an implementation of FE applications based on CNT paste such as X-ray tube, field emission lamp (FEL) etc is performed by glass or ceramic vacuum sealing techniques. However the vacuum packaging using glass or ceramic has a high processing temperature induced a drastic thermal degradation of CNT emitters : The Glass vacuum sealing is performed at around 500 °C in air ambient with oxygen and the ceramic vacuum sealing using brazing technique is processed at around 1,000 °C in vacuum. In this study, we have developed a highly thermo-stable CNT emitter with high FE performance by optimization of CNT paste composition. First of all, the optimizing process of CNT paste was investigated in terms of surface morphology with intensified adhesion to achieve highly reliable CNT emitters. And simultaneously, in order to obtain a stable FE performance after the high temperature sealing process, we have designed and developed novel inorganic fillers in terms of an anti-reaction by self gettering effect. We found that a developed nano-scale inorganic composite with the optimized paste composition can strongly improve the thermo-stability and reliability of CNT emitters. And by maximizing the number of activated CNT emitters which contributed to the field emission from our optimized paste design, very excellent FE characteristics could be also implemented at the same time. The developed CNT emitters with self gettering effect were observed to maintain the FE properties after the high-temperature process both in air(at 500 °C) and in vacuum(at 1,000 °C), showing a very high emission current density of over 30 mA/cm2 at an applied field of 2.1 V/μm. The I-V characteristic and the SEM observation was showed nearly same properties in the status of CNT emitters before and after the high-temperature process. Therefore, the developed CNT emitters can be directly used in various FE applications by the utilized vacuum sealing process at a high-temperature.