电泳法制备场发射阴极的性能优化研究

Optimization of Field Emission Properties of Cathodes by Electrophoretic Deposition

电泳法是一种新型的大面积碳纳米管场发射阴极制备方法。文章在成功地用电泳法制备了适用于场发射显示器的碳纳米管阴极基础上,通过选用不同的碳纳米管原料、改变电泳条件等方法,进一步优化碳管阴极的性能。使用不同方法制备的碳纳米管配置电泳液,由于制备方法和碳管本身的特性,管子在电泳溶液中呈现不同的分散性。碳管管径较粗时由于表面自由能相对小,所以碳管在溶液中不易形成团聚物,电泳沉积的阴极会均匀平整;管径小的碳管则由于容易团聚,需要加入表面活性剂来改善其在电泳溶液中的分散性。场发射特性和发光显示图实验结果发现,即使得到相同均匀平整的阴极,但是由于碳管本身的发射能力的差异性最终导致电泳沉积得到的阴极的场发射特性的不同。另外,电泳的实验条件也会对沉积的阴极的场发射性能和形貌产生影响。在不同电泳直流电压条件下,碳管薄膜的密度分布和厚度不同,呈现出不同的场发射能力,结果表明当电压值在25V时可以得到性能最佳的场发射阴极。

Electrophoretic deposition（EPD）method has many advantages,such as short formation time,simple deposition apparatus,low cost and suitability for mass production as in electric coating industry.EPD is superior to screen printing in preparing large scale field emission cathode.Carbon nanotubes（CNTs）synthesized by different methods were applied to fabricated CNTs film cathodes.In order to get better field emission cathode,CNTs synthesized by different methods were compared and the conditions of EPD were optimized.The cathodes were characterized by scanning electron microscopy,I-V and luminescence image measurements.It is found that the emission uniformity of the cathode depends on the dispersibility of the tubes in the electrophoretic solution.Uniform cathode could be obtained when CNTs with bigger diameter are used in EPD,because they have better dispersity in solution than smaller CNTs.The field emission properties of as-grown cathodes are determined by the emission capability of the CNTs used.The influence of the voltage in the electrophoretic process on the uniformity of the CNTs film distribution was also studied.The results indicate that the uniformity of CNTs film and optimized emission properties of the cathode can be achieved when the voltage is 25 V.