【作者】 曹章轶；

【导师】 孙卓；

【作者基本信息】 华东师范大学 ， 凝聚态物理， 2006， 硕士

【摘要】 碳纳米管(CNTs)的发现，引起了全世界众多科学家的广泛关注。碳管具有优异的电学、力学性能，可以在许多领域得到应用。尤其是它具有大的长径比，低的功函数，良好的导电性和纳米级的尖端，使其能够在相对较低的电压下就能长时间地发射电子，因此被认为是一种优良的场致发射阴极。碳管已经应用于诸如扫描电子显微镜和透射电子显微镜等高分辨率电子束器件，并有望在场致发射平面显示器中得到广泛的应用。 本文采用低温低压化学气相沉积(CVD)方法在金属衬底上直接生长碳纳米管薄膜，并分别运用薄膜和厚膜工艺，制作场发射阴极。研究了沉积工艺、后处理工艺等对碳纳米管薄膜场致电子发射性能的影响。 本文主要研究结果如下： 1 丝网印刷碳纳米管场发射阴极的场致电子发射性能研究 1) 在一定的生长条件下，沉积60min，在镍片衬底上生长出管径较大、取向无序、分布均匀、结构缺陷较多的多壁碳纳米管。运用丝网印刷技术，制成场发射阴极。 2) 讨论了乙炔流量，镍片上下表面和碳管与有机浆料的浓度比对碳纳米管形貌、结构和场发射性能的影响。结果表明，不同条件下制备的碳纳米管阴极场发射性能有很大的差异。保持压强(2×10~3pa)、氢气的流量(200sccm)、沉积时间(60min)、温度(550℃)不变，当乙炔流量为70sccm，碳管与有机浆料的浓度比为1g／8ml时，在镍片上表面生长的碳管，场发射性能最好，开启电场为4.19V／μm，在5.88V／μm的电场下，电流密度为37μA／cm~2，发射点较多，密度为10~3／cm~2。 3) 对以上工艺条件的阴极进行后续退火处理。在氧气气氛，温度300℃，时间8min的退火条件下，开启电场降至3.95V／μm，电流密度升至43μA／cm~2，发射点增多，密度为2×10~3／cm~2，分布比较均匀。经扫描电镜观察，此时碳管的密度适中，碳管之间的屏蔽效应被有效抑制。因此得出结论：退火处理能改变阴极表面碳管的密度，提高阴极的场发射性能。 2 衬底直接生长碳纳米管场发射阴极的场致电子发射性能研究 1) 在一定的生长条件下，沉积5min，在镍片衬底上生长出管径较小、取向无序、分布均匀、结构缺陷较多的多壁碳纳米管，将覆有碳管的镍片直接作为场发射阴极。 2) 讨论了乙炔流量和沉积时间对碳纳米管形貌、结构和场发射性能的影响。结果表明，不同条件下制备的碳管阴极场发射性能有很大的差异。保持压强(2×10~3pa)、氢气的流量(200sccm)、温度(550℃)不变，当乙炔流量为50sccm，沉积更多还原

【Abstract】 The discovery of carbon nanotubes (CNTs) attracts many scientists’ attention. CNTs can be used in many fields due to its excellent properties of mechanics, electricity. CNTs has a high aspect ratio, low work function, good electrical conductivity and nanometer tip, which can emit electrons at low voltage. So CNTs is considered as a good field emission cathode and has been used in electron beam device such as SEM and TEM. It is believed that CNTs will have a widely application in field emission display.In this paper CNT film was deposited on metal substrate by low temperature and low pressure chemical vapor deposition (CVD). Field emission cathode was made by thin-film and thick-film process. By varying deposition and processing conditions, the optimized conditions for field electron emission were found.The major results are listed as follows.1 Field emission properties of CNTs cathode made by screen printing1) Thick CNT film was grown on nickel plate for 60 minutes at a certain condition. CNTs has a large diameter and is grown uniformly and randomly oriented with many defects. Field emission cathode was made by screen printing.2) By varying conditions such as acetylene flow rate, concentration ratio of CNTs and organic binder, CNTs deposited on different surfaces of nickel plate, the optimum condition for electron field emission was found. When acetylene flow rate was 70sccm, concentration ratio was 1g to 8ml, the field emission properties of CNTs deposited on the surface of nickel plate were the best. At this condition, turn-on field of 4.19V/μm, emission current density of 37μA/cm~2 at the field of 5.88V/μm and emission spot density of 10~3/cm~2 were achieved.3) Annealing processing was used to increase the field emission properties of CNT cathode. At the temperature of 300°C for 8 minutes heat treatment in the ambient, the field emission properties of CNT cathode were the best. At this condition, turn-on field of 3.95V/μm, emission current density of 43μA/cm~2 and emission spot density of 2×10~3 /cm~2 were achieved. CNTs density on cathode surface was decreased so as to eliminate screening effect between CNTs. So CNTs density can be changed by annealing processing and the field emission properties of CNT cathode were improved.2 Field emission properties of CNT film on nickel plate as field emission cathode更多还原