【作者】 郑新亮；

【导师】 白晋涛；

【作者基本信息】 西北大学 ， 光学， 2009， 博士

【摘要】 场发射显示器件具有非常突出的优点:体型纤薄、画质优良、视角宽阔、响应迅速、便于数字化控制、抗电磁干扰能力强等,被认为是取代CRT的理想平板显示器件。碳纳米管长径比很大、化学稳定性好、熔点高,是一种理想的场发射电子源。利用丝网印刷或涂敷工艺可以方便地制备出无序碳管薄膜,而且成本很低,易于量产,适合制作大面积显示器。但是,按照这种工艺制备的碳管薄膜的场发射能力、均匀性和稳定性都有待进一步提高。由于目前合成技术的限制,制备具有特定功能的碳管成本较高,难度较大,通过适当方法对碳管表面进行改性是一个提高其场发射能力的捷径。本论文围绕丝网印刷和涂敷法制备的多壁碳管薄膜场发射性能的改善,完成了以下主要工作:(1)采用CVD方法成功制备了MWCNTs。对丝网印刷工艺制备的二电极和三电极结构FED的场发射能力进行了对比,证实三电极结构优于二电极结构。粉末涂敷法制备的碳管阴极薄膜场发射性能优于浆料印刷法,但其发射的稳定性不理想。(2)变温电阻率测试和场发射性能实验表明:MWCNTs薄膜的电阻率具有明显的负温度热敏特性(温度越高,电阻率越小)。其场发射性能易受环境温度影响,温度升高,场发射能力增强。这可能源于MWCNTs功函数的降低、参与场发射碳管β因子分布的展宽、Ag/MWCNTs界面电输运特性的变化以及阴极薄膜的局部高温等因素。这一工作提示碳管薄膜型FED的设计和开发要注意控制温度效应。(3)采用248nm的KrF准分子脉冲激光对丝网印刷的MWCNTs薄膜进行了激光烧蚀处理,发现特定能量的激光烧蚀处理能够降低碳管场发射开启电压、增加发射电流,有效改善碳管阴极薄膜的场发射性能,但过高能量(大于165mJ)的激光处理会抑制MWCNTs的场发射。其作用机制可以理解为“光烧蚀作用”和“热烧蚀作用”两种效应。激光处理改性碳管薄膜的方法新颖简便,不接触样品,易于定量控制和工业应用,具有一定创新性,目前相关研究报道尚不多见。(4)直接给碳管浆料中添加纳米Ni粉后,样品导电能力增强。Ni-MWCNTs薄膜场发射能力有所提高,但并不显著。用化学还原反应的方法给MWCNTs包覆Ti原子/团簇的实验,较难控制样品中的有效成份,场发射性能表现不佳。(5)用磁控溅射方法给MWCNTs样品表面溅射适当厚度Ti膜,样品表面导电性得到改善,场发射能力显著提高。场发射开启电压大幅降低,发射电流激增,尤其是镀膜样品表现了非常良好的时间稳定性。用磁控溅射镀Ti改性碳管的处理方法,不引入其它杂质,可以很好地控制场发射改良效果,而且成本较低,便于量产。(6)利用数值模拟的方法,研究了的三电极平栅极结构单一像素的场发射显示性能与器件几何结构之间的关系。发现较大沟槽倾角增强了阴极场发射能力,同时又限制了电子轰击阳极的运动,降低了效率,取倾角为45°较为理想。阴、阳极间距也强烈的影响像素的显示质量。该工作为碳管薄膜平栅极器件的设计提供了一点有益的参考。更多还原

【Abstract】 The FED possess many distinct properties, such as thin panel thickness, excellent image quality, wide viewing angle, quick response, easy to implement digital control, free from the terrestrial magnetic effect etc. As a novel flat-panel display, the FED has been regarded as a promising competitor to the CRT. Carbon nanotube (CNT) is prefect field emission electron source due to their high aspect ratio, well chemical stability and higher melting point. CNTs film is easy to be prepared using screen-printed or coated method which is fit for large area display. CNTs film in this way has low cost and suitability for mass production. However, its field emission performance, Stability and uniformity need further improvement. The synthesis CNTs with certain function is hard to realize for its high cost and technical difficulty. The modification of CNTs surface in suitable way is a shortcut to improve field emission function.In this paper, we mainly discuss how to improve field emission function of multi-walled carbon nano-tubes (MWCNTs) film using screen-printed or coated method. Main conclusion and innovative results are presented as follow:(1) The MWCNTs film successfully is synthesised by CVD method. We studied the field emission performance of diode and triode structure prepared by screen-printed method. The result shows that triode structure excels diode structure at function. We also found that the coated method is better than screen-printed in field emission performance, whereas the current is not enough to be stable.(2) The temperature dependence of the resistance and field emission are investigated and show that the resistance of MWCNTs film becomes smaller and emission performance is better with temperature increment. This result can be attributed to somefactors, such as the work function,βfactor distribution broadening, and transportcharacteristics of electrons at interface of Ag/MWCNTs as well as local hyperthermia. Thus the temperature effect needs to be considered in design of CNTs-FED.(3) The surface treatment of screen-printed MWCNTs emitters using a 248nm (KrF) excimer laser are investigated. The field emission characteristics of MWCNTs are measured following laser irradiation. The results show that the turn-on voltage and the current are highly dependent on the value of the laser fluence. The laser treatment are able to improve the field emission characteristics of MWCNTs, however electron emission are impeded when the energy is higher than 165mJ. This result can be interpreted by photo ablation and thermal ablation mechanisms. The laser treatment is novel and easy to carry out in modification of CNTs film. It provides a precise degree of control over the treatment process which is seldom found.(4) The conductivity of MWCNTs film is increased by doping nickel powders.The field emission performance is improved but not obviously. Coating of MWCNTs was carried out by Ti atom/cluster from chemical reduction. This method results in poor emission performance due to organic matter and other impurity.(5) The field emission performance and conductivity are obviously improved after MWCNTs film deposited a thin layer of titanium. The turn-on voltage evidently decreases. The current increase distinctly and has long time stability. This way improve effectively field emission performance and produce no impurity. It also has low cost and suit for mass production.(6) Emitted current distribution and electron trajectories of individual pixel with the planar gate structure are studied by numerical simulation method. A greater slope angle of the gate-cathode groove enhances emission ability of the cathode, while influences electron trajectories and decreases the display efficiency. 45°is a better choice balanced the two factors. The display quality is gravely affected by the anode -cathode distance.更多还原