电化学刻蚀法制备LaB_6场发射微尖锥阵列

Fabrication of LaB_6 Tip Field Emission Arrays Using Electro-chemical Etching Method

采用电化学刻蚀方法,成功制备出单尖的六硼化镧、钼、钨及钨铼合金场发射冷阴极尖锥,并对这几种场发射单尖锥阴极的电子发射性能进行了测试比较。结果表明,LaB6作为场发射阴极,具有良好的发射性能和稳定性。在〈111〉面单晶LaB6基片上,用PECVD法沉积非晶硅作掩膜,制备出具有一定高度的LaB6微尖锥场发射阵列,结果发现,LaB6基底较为平整,尖锥阵列呈现出各向异性。该结论对LaB6材料在场发射阴极方面的进一步研究具有重要的指导意义。

At present, field emitting cold cathode materials, including molybdenum, silicon, diamond carbon films, diamond-like carbon films and carbon nanotubes, are being developed. With each of these materials having their own shortages, it is important to seek some new field emitting cold cathode materials. Lanthanum hexaboride （LaB6） is a material with low work function, low resistivity, low sputtering yield, high melting point and high chemical stability. It has been widely used as thermionic emitters. On the other hand. LaB. is also an excellent material for use as field emission cathodes. Some field emitting cold cathode single tips including LAB6, molybdenum, tungsten and tungsten rhenium were fabricated by using electro-chemical etching method. The electron emission characteristics of these cold cathodes were studied in a diode test cell in vacuum system. Changing the anode voltage at a pressure of 1 × 10^-3 Pa, the current density of single crystal LaB6 was compared with other material cathodes. It showed that LaB6 was one kind of excellent materials to act as field emitting cold cathode, whose current density was much higher than any other materials. In addition, LaB6 field emission arrays were attempted to be fabricated by using electro-chemical etching method. The a-type silicon layer was depositing by PECVD as mask. Electrolytes in this process were ethanol （CH3CH2OH） containing 2% hydrochloric acid （HCI） and the electrolytic current was 0.6 mA. The SEM showed that the substrate and surface of single crystal LaB6 tips were both smooth. The height of LaB6 tips was about 1.7 μm. The uniformity of the tips was fine, while due to the erosion selectivity for different crystalloid surface in electrochemical etching method, serious anisotropic phenomenon was observed for LaB6 tips. It demonstrated that, seeking some new electrolytes or using other special dry etching methods instead of wet etching methods, maybe effective to fabricate excellent LaB6 field emitting cold cathode tips. These experimental conclusions were constructive to direct the application of LaB6 to field emission cathodes further.