类球状微米金刚石聚晶膜场发射的稳定性

The Field Emission Stability of Globe-like Diamond Microcrystalline Aggregates

在覆盖金属钛层的陶瓷上,利用微波等离子体化学气相沉积(MPCVD)法制备出类球状微米金刚石聚晶膜。通过二极管结构测试了聚晶膜的场致电子发射特性,利用扫描电子显微镜、拉曼光谱、XRD分析了场发射前后薄膜的结构和表面形貌的变化。发现在高场、大电流密度的场发射中,对类球状微米金刚石聚晶薄膜中的金刚石聚晶颗粒影响很小,而对金刚石聚晶颗粒间的非晶碳层影响很大。对类球状微米金刚石聚晶变化机理进行了研究。

The globe-like diamond microcrystalline aggregates were fabricated by microwave plasma chemical vapor deposition （MPCVD） method. The ceramic with a Ti mental layer was used as substrate. The fabricated diamond was evaluated by Raman scattering spectroscopy, X-ray diffraction （XRD） spectrum, scanning electron microscope （SEM）. The results led to the conclusion that the obtained film consists of crystalline diamonds structures. The field emission properties were measured by using a diode structure in vacuum. A phos- phor-coated indium tin oxide （ITO） anode was used for observing and characterizing the field emission. The field emission characteristics of the fabricated diamond was studied under low electric field （〈3 V/μm） and high electric field （〈5 V/μm）, respectively. The Fowler-Nordheim （F-N） plots corresponding to the curves of the low electric field and the steady operation circles in the high electric field are almost straight line, which indicated that the mechanism of the electron emission from the diamond microcrystalline aggregate is linked to the tunnel effect. It was found that the globe-like diamond microcrystalline-aggregates exhibit good electron emission properties, but the microstructure and electrical conductivity have large change before and after the field emission. The good emission properties of the diamond aggregates could be considered to be combined results from the lots of the grain boundaries in the diamonds microcrystaUine aggregates. After the field emission, the amorphous carbon become thinner and the globe-like diamonds are not damaged. When the amorphous carbon films are stable, the field emission current could be stabilized accordingly. The results indicated the globe-like diamond has excellent emission characteristics.