电泳和电镀法增强碳纳米管场发射特性的研究

Field Emission Enhancement of Carbon Nanotubes Assembled by Electrophoresis and Successive Electroplating

碳纳米管(CNT)和衬底的电学接触问题是获得高性能CNT电子器件的一个关键性的问题。本文采用电泳电镀方法制备CNT冷阴极,有效改善了CNT与衬底间接触电阻,增强了碳纳米管场发射性能。电泳电镀法制备的碳纳米管冷阴极场发射的开启电场(电流密度为10μA.cm-2时的电场)由2.95 V.μm-1降低到1.0V.μm-1,在电场为8V.μm-1时电流密度由0.224增加到0.8112mA.cm-2。在电流密度为800μA.cm-2时进行1h的场发射稳定性测试,结果表明,电泳电镀法所得CNT场发射电子源电流密度几乎不变,而且电流密度比较稳定;而只有电泳的方法获得的CNT场发射电子源电流密度波动较大,电流不稳定且呈较快的衰减趋势,1h后减少到原来的75%。采用电泳电镀方法制备CNT阴极,CNT的根部被纳米银颗粒覆盖和包裹,使CNT与衬底接触更加牢固而紧密,又由于银具有很好的导电性,从而大大减小了接触电阻,因此电泳电镀法能大大改善CNT与衬底的电学接触性能。

A novel technique was successfully developed to assemble carbon nanotubes （CNTs）, coated with Ag nano-particles,on glass substrate by a combination of electrophoresis and successive electroplating.The microstructures of the CNTs emitter assembly were characterized with scanning elctron microscopy （SEM） and energy dispersive spectroscopy （EDS）. The influence of the two emitter fabrication techniques on field emission characteristics was studied. The results show that newly- developed technique considerably improves its emission properties. For instance, the onset voltage drops from 2.95V·μm-1 to 1.0V·μm-1 at an emission current density of 10μA·cm-2;and at 8V＇tma-1 ,the emission current density rises up from 0.224 to 0.8112 mA＇cm-2,remaining steady for at least 1h, possibly because of low electrical resistance at the interface of Ag coated CNTs and the substrate. However, the emission current density of the emitter, assembled by electrophoresis only, fluctuates too much, decaying by 25 % after one hour.