中文摘要：

在超高真空系统中对基于丝网印刷方法制备的碳纳米管薄膜的场蒸发效应进行实验研究.实验发现,碳纳米管薄膜样品存在场蒸发现象,蒸发阈值场在10.0—12.6 V/nm之间,蒸发离子流可以达到百皮安量级;扫描电子显微镜分析和场致电子发射测量结果表明,场蒸发会使碳纳米管分布变得更加不均匀,会导致薄膜的场致电子发射开启电压上升（240→300 V）、场增强因子下降（8300→4200）、蒸发阈值场上升（10→12.6 V/nm）,同时使得薄膜场致电子发射的可重复性明显变好.场蒸发也是薄膜自身电场一致性修复的表现,这种修复并非表现在形貌上,而是不同区域场增强因子之间的差距会越来越小,这样薄膜场致电子发射的可重复性和稳定性自然会得到改善.

英文摘要：

In recent years,the carbon nanotube（CNT） emitters used for ion sources or gas sensors have been investigated,and the progress of several approaches such as field ionization and field desorption sources has been reported.However,a major concern for these applications is possible loss of CNTs caused by field evaporation,which can shorten the lifetimes of CNT-based emitters used for high electric field ion sources.So in CNT-based field emitter technology,emitter lifetime and degradation will be key parameters to be controlled.However,up to now only very few investigations in this direction have been conducted.The reason for this might lie in the fact that one often considers that the threshold value of field evaporation for a kind of material（ 40 V/nm） is much higher than the field of ionization or desorption（ 10 V/nm） according to the metal material characteristics（such as the threshold values of field evaporation for tungsten and molybdenum are 54 V/nm and 45 V/nm,respectively）.In this work,the carbon nanotube thin-film（the density of CNTs is about 2.5 × 10~8/cm~2） is fabricated by screen-printing method,and the field evaporation behavior of CNT thin-film is studied experimentally in an ultrahigh vacuum system typically operating at a pressure of lower than 10 9Torr after a 4-hour bake-out at ~200？C.Unlike the vertically aligned CNT array having higher electric field around the edge of the array because of the shielding effect,the printed CNT thin-film has more uniform distribution of electric field and is very easy to relize the mass production.The results show that the prepared CNT thin-film has quite obvious field evaporation behavior（some contaminants have deposited on the surface of grid after field evaporation,and energy-dispersive X-ray spectroscopy elemental mapping result of the grid indicates that the contaminants consist mainly of carbon elements）,with turn-on field in a range of 10.0–12.6 V/nm,ion current could reach up to hundreds of p A.Meanwhile,the results with scanning