提高钼尖锥场致发射阵列阴极发射性能的研究

Improvement of Emission Performance of Molybdenum Field Emission Arrays

在利用微细加工技术和双向薄膜沉积工艺制得的钼尖锥场致发射阵列阴极进行实用化的过程中,目前存在的两个主要障碍是,阴极发射电流密度低和工作不稳定。通过对阴极发射失效机理和失效阴极的SEM照片进行研究认为,导致电流密度较低的原因是由于尖锥阵列的不均匀性造成只有部分尖锥发射电子;引起发射不稳定的主要因素是由于尖锥表面的微凸起和毛刺以及它吸附的各种影响有效功函数的污染物。采用电阻限流技术提高了阵列发射的均匀性,同时通过阴极老炼技术增强了场发射的稳定性,使其电流发射密度有很大程度的提高,而且电流波动也大为减小。研究结果对于该阴极在射频功率和平板显示等器件上的应用有着重要的意义。

Low emission and emission instability are still two main obstacles in applying field emission arrays by micro-manufacture and thin-film technology to actual devices. By analyzing the SEM photographs of the destroyed chips, the low emission could be attributed to non-uniformity of emission tips in the array, and the emission instability was caused by the contamination and micro-protrusion on the tip surface. Buffering resistor was used to enhance emission uniformity, by which the emission current density was increased greatly. Pulse and DC ageing processes were adopted in the early testing to improve emission stability and it indicated that pulse ageing was better and more efficient. Both buffering resistance and ageing processes were not only effective on stable emission but also could even in-crease emission current to some extent. With buffering resistance technique and ageing process, the emission current of FEA increased by 43 % and 50 % in DC and pulse test respectively, and the emission current fluctuating was considerably decreased. Coating protective materials such as nanocrystalline diamond on emission surface was also an effective way to improve performance of FEAs and more research needs to be done. All the work above was very significant in applying FEAs to radio frequency power devices and field emission displays.