三极场发射显示器中二次印刷型碳纳米管阴极的制备及特性(英文)

结合丝网印刷技术,研发了一种碳纳米管阴极制备法.利用双壁纳米管作为原材料,并加入细小银颗粒,制作了混合纳米管浆料.将混合纳米管浆料制作在传导电极表面,再将普通纳米管浆料印刷在混合纳米管浆料的上面.在链式烧结炉中对烘烤后的纳米管浆料同时进行烧结以除掉有机溶剂.在进行适当的后处理工艺之后,就形成了二次印刷型纳米管阴极,它能显著改善阴极的场致发射特性.制作了二次印刷型纳米管阴极的三极结构场致发射显示器.该显示器具有更高的发光亮度以及更好的发光图像亮度均匀性.与普通纳米管阴极场致发射显示器相比较,它能够将开启电场从2.15V/μm降低到1.75V/μm,并能够将最大场发射电流从735.8μA提高到1 588.5μA.所研发的纳米管阴极制备方法具有很强的实际应用性,且制作成本低廉.     

具有石墨烯/铟锑氧化物复合透明电极的GaN发光二极管

近年来,石墨烯材料由于优异的光电性能获得了广泛关注,并应用于发光二极管的透明电极以取代昂贵的铟锑氧化物(indium tin oxide, ITO)透明电极,但由于石墨烯与p-GaN功函数不匹配,二者很难形成好的欧姆接触,因而造成器件电流扩展差和电压高等问题.本文将ITO薄层作为石墨烯透明电极与p-Ga N间的插入层,以改善石墨烯与p-Ga N层的欧姆接触.所制备的石墨烯透明电极的方块电阻为252.6?/□,石墨烯/ITO复合透明电极的方块电阻为70.1?/□;石墨烯透明电极与p-Ga N层的比接触电阻率为1.92×10~(–2) ?cm~2,ITO插入之后,其比接触电阻率降低为1.01×10~(–4) ?cm~2;基于石墨烯透明电极的发光二极管(light emitting diode, LED),在20 m A注入电流下,正向电压为4.84 V,而石墨烯/ITO复合透明电极LED正向电压降低至2.80 V,且光输出功率得到提高.这归因于石墨烯/ITO复合透明电极与p-Ga N界面处势垒高度的降低,进而改善了欧姆接触;另外,方块电阻的降低,使得电流扩展均匀性也得到了提高.所采用的复合透明电极减少了ITO的用量,得到了良好的欧姆接触,为LED透明电极提供了一种可行方案.     

碳纳米管/膨润土复合膜的附着性能及场发射性能

碳纳米管(CNT)阴极膜与基底的附着性能严重影响场发射的均匀性和稳定性.提出一种制作CNT/膨润土(BP)复合膜的方法.通过添加纳米尺度BP作为填料,使BP与CNT间产生插层效应,进而减小CNT膜的间隙势牟,改善CNT与基底间的接触性能.测试结果显示,CNT/BP复合膜与基底的附着性能得到明显改善,并且使场发射均匀性和...     

六角密排多迭层碳纳米管阴极的大电子发射电流和高电子发射稳定性（英文）

研制了一种六角密排多迭层碳纳米管阴极.在这种结构中,衬底银电极由烧结的银浆制作在透明锡铟氧化物电极上,且具有六角形边缘,相邻衬底银电极交错排列于阴极面板上.用ZnO和SnO_2颗粒作为掺杂材料,在衬底银电极和单一碳纳米管层之间制作了底部混杂层;单一碳纳米管层中的碳纳米管主要被用于发射阴极电子.给出了六角密排多迭层碳纳米管阴极的制作工艺,并研究了六角密排多迭层碳纳米管阴极用于电子源的可行性.将氮气作为保护气体,采用烧结方法除掉制备浆料中的有机粘合剂及其它有机杂质.将六角密排多迭层碳纳米管阴极真空密封进三极场发射显示器中,能够形成稳定的电子发射电流.测试结果表明,与普通碳纳米管阴极相比,六角密排多迭层碳纳米管阴极具有更优的电子发射特性,其开启电场为1.83V/μm,最大电子发射电流为2 718.6μA;且其具有良好的电子发射曲线趋势,当电场强度从2.17V/μm增强到3.06V/μm时,电子发射电流的增幅约为1 410.3μA.对电子发射电流随时间的波动变化进行了测试,测试结果显示六角密排多迭层碳纳米管阴极具有可靠且稳定的电子发射电流.绿色发射图像表明六角密排多迭层碳纳米管阴极具有良好的电子发射均匀性及高的电子发射亮度.鉴于其简单的制作结构和制作工艺,六角密排多迭层碳纳米管阴极具有一定的实际应用性.     

注入和输运对单层有机发光器件复合发光的影响

通过分析聚合物电致发光器件中载流子注入、输运、激子的解离与复合过程,提出了激子解离与复合的理论模型. 基于电流连续性方程和Poisson方程,给出了激子复合密度、电流密度及复合效率表达式.研究两电极与有机层之间在Ohmic和Fowler-Nordheim接触条件下载流子迁移率对器件中激子的复合密度及外加电压和注入势垒对器件电流和复合效率的影响.结果表明:1)在一个较宽的注入势垒和迁移率范围内,复合密度不是由两个注入电极的相对注入比决定而是由有机层电子和空穴迁移率之比所支配;2)固定阴极势垒,而阳极势垒由小变大时,器件电流由接触限制向空间电荷限制转变;3)复合效率随外电压升高先增加,当电压达一临界值时而陡降,存在一个最佳的注入势垒值.结果说明:电极与有机层的能带匹配及有机层间的迁移率匹配对器件复合发光有着极其重要的影响.其计算值与所报道的理论结果相符.     

增强碳纳米管场发射性能的沟槽形冷阴极制作(英文)

基于烧结工艺和丝网印刷技术,研发了一种新的沟槽形冷阴极.底部绝缘层由黑色绝缘浆料被烧结后制成,且在底部绝缘层中存在倾斜面.将银浆丝网印刷在条形电极上,依次经烘烤和烧结工艺后形成银电极.利用细砂纸,对银电极进行适当的抛光工艺,以便获得光滑的电极表面.由于特有的银电极形状,从而易于获得更大的场增强因子.将碳纳米管制备在银电极上,形成场发射极.致密的碳纳米管层完全覆盖银电极表面,特有的边缘场增强效应能够使得碳纳米管发射出更多的电子.顶部绝缘层则用于抑制碳纳米管的横向电子发射.结合沟槽形冷阴极,制作了三极结构的场致发射显示器,该显示器具有良好的场致发射特性及优良的发光图像均匀性.与普通冷阴极场致发射显示器相比,沟槽形冷阴极场致发射显示器能够将开启电场从1.86V/μm降低到1.78V/μm,将最大场致发射电流从1 537μA增加到2 863μA,且将最大发光图像亮度从1 386cd/m2提高到1 865cd/m2.该制作技术在场致发射显示器中具有较强的实际应用性.     

基于丝网印刷技术的碳纳米管场发射冷阴极制作

制备了一种新型碳纳米管浆料,并总结了一套阴极制作工艺.实验表明,质量比约为10%的纯化碳纳米管、5%的纳米金属粉末和有机材料混合形成的印刷浆料,其阴极具有较好的发射均匀特性.在浆料制备过程中通过加入表面活性剂使碳纳米管分散更加均匀.用丝网印刷技术制作阴极,并用机械刀刻的办法制作阴、栅两极之间的沟槽,经烧结后分析阴极膜的电阻率和粘附性随阴极材料组分和制作工艺的变化关系,确定较为合适的升温曲线及丝网目数,阴极碳纳米管的均匀性、导电性的提高改善了发射均匀性.该阴极开启场为2.5 V/μm,在电场强度为3.3 V/μm下,阳极电流为5.6 μA,场发射电流稳定,波动小于5%.     

导电高分子场发射特性研究

用掺杂樟脑磺酸的聚苯胺(PANI-CSA)形成的导电高分子制成的薄膜作为场致发射的阴极材料,用覆盖了荧光层(ZnO：Zn)的氧化铟锡(ITO)做阳极,由所制成的显示器件得到比较稳定的场致电子发射,并具有较低的场发射阈值电压。通过研究导电高分子薄膜形貌,初步分析了场发射电流机制。认为导电高分子薄膜产生场发射的原因是薄膜在高电场作用下,首先在平整的高分子薄膜表面形成了尖锥和凹陷,提高了场强增强因子(β)。     

印刷制作的双半导体底层碳纳米管薄膜阴极的稳定电子发射

应用带保护气进行烧结的方法,制作了一种双半导体底层碳纳米管薄膜阴极.利用烧结的银浆形成条形银电极,在条形银电极表面制作了具有相同宽度且平行排列的ZnO掺杂底层和TiO2掺杂底层,在掺杂底层上面制备了碳纳米管膜层.由于保护气的防氧化屏蔽,碳纳米管膜层中的碳纳米管未受损害,ZnO粒子和TiO2粒子也在烧结过程中得到了很好地保护,双半导体底层碳纳米管薄膜阴极获得更优的电子发射特性,且电子发射稳定性也得到有效增强.与普通条形银电极碳纳米管阴极相比,双半导体底层碳纳米管薄膜阴极能够将开启电场从2.09V/μm降低到1.91V/μm,将最大电子发射电流从1 653.5μA提高到2 672.9μA.在2.69V/μm电场作用下,普通条形银电极碳纳米管阴极的电子发射电流仅为421.1μA,而双半导体底层碳纳米管薄膜阴极的电子发射电流能够达到723.5μA.从发射电流稳定性实验曲线可以看出,双半导体底层碳纳米管薄膜阴极实现了稳定的电子发射,表明ZnO掺杂底层和TiO2掺杂底层能够应用于真空环境.利用数码相机获得了具有良好质量的发射图像,验证了双半导体底层碳纳米管薄膜阴极制作的可行性和适用性.     

大电流稳定发射铁电阴极的模拟与实验研究

讨论了铁电阴极的发射机理, 借助MAFIA对不同电极结构的铁电阴极表面电场分布进行了模拟计算. 计算中发现, 发射面电极结构对铁电阴极表面三界点处的场增强效应影响很大,特别是具有孤岛电极结构的铁电阴极具有更大的三界点场强,从而获得更大和更稳定的发射电流. 通过对电极结构及其工艺的改进,使用PLZT铁电阴极在实验中得到了大于100A的电流.     

Effect of sputtered Cu film’s diffusion barrier on the growth and field emission properties of carbon nanotubes by chemical vapor deposition

Growth of carbon nanotube (CNT) films with good field emission properties on glass is very important for low cost field emission display (FED) applications. In addition to Ni, Co and Fe, Cu can be a good catalyst for CNT growth on glass, but due to diffusion into SiO₂ it is difficult to control the CNTs density and uniformity. In this paper, four metal barrier layers (W, Ni, Cr, Ti) were deposited by dc magnetron sputtering on glass to reduce the Cu diffusion. As-grown CNT films showed various morphologies with the use of different barrier metals. CNTs with uniform distribution and better crystallinity can be synthesized only on Ti/Cu and W/Cu. Voltage current measurements indicate that better field emission properties of CNT films can be obtained on titanium and tungsten barriered Cu, while chromium and nickel are not suitable barrier candidates for copper in CNT-FED applications because of the reduced emission performance. PACS 81.05.Uw; 61.46.Fg; 85.45.Db; 66.30.-h     

碳纳米管和天鹅绒阴极强流发射特性的对比研究

采用电泳沉积法、碳纳米管纸和化学气相沉积直接生长法制备了三种碳纳米管阴极. 从强流发射性能、阴极等离子体膨胀、阴极起动、发射均匀性、工作稳定性以及脉冲放气特性等多个方面, 对比研究了碳纳米管阴极和化纤天鹅绒阴极的强流发射特性, 研究表明碳纳米管阵列和碳纳米管纸阴极发射性能明显优于普通化纤天鹅绒, 碳纳米管阴极发射性能与碳纳米管取向无关, 管壁的缺陷发射对无序碳纳米管阴极强流发射具有重要贡献. 碳纳米管阴极的起动场强约为普通化纤天鹅绒的2/3, 电场上升率相同时碳纳米管阴极比化纤天鹅绒阴极起动时间短12–17 ns. 碳纳米管阴极发射均匀性优于化纤天鹅绒, 尤其是碳纳米管阵列, 整个阴极表面等离子体光斑致密且均匀. 在二极管本底气压为6×10^-3 Pa时, 碳纳米管纸阴极对应的二极管峰值气压不到0.3 Pa, 约为普通化纤天鹅绒阴极的1/5, 碳纳米管阵列阴极放气量在三种阴极中最少, 仅为0.042 Pa. 结果表明, 碳纳米管阴极在强流电子束源和相关高功率微波器件领域具有潜在的应用价值.     

Field emission properties of carbon nanotube film using a spray method

We fabricated carbon nanotube (CNT) emitters by a spray method using a CNT suspension with ethanol. Indium with a low melting pointing metal or indium tin oxide (ITO) was deposited on the glass substrate. The CNTs were sprayed on these layers and thermally annealed. The sprayed CNTs on an ITO were obtained a high emission current density, field enhancement factor, and a uniform emission pattern than the sprayed CNTs on an ITO layer. We found that the sprayed emitters on the indium layer had good field emission characteristics because of the strong adherence between the metal layer and CNTs.     

Hole Injection Enhancement of MoO_3/NPB/Al Composite Anode

An ultra-thin molybdenum(VI) oxide(MoO_3) modification layer can significantly improve hole injection from an electrode even though the MoO_3 layer does not contact the electrode. We find that as the thickness of the organic layer between MoO_3 and the electrode increases, the hole injection first increases and it then decreases.The optimum thickness of 5 nm corresponds to the best current improvement 70%, higher than that in the device where MoO_3 directly contacts the Al electrode. According to the 4,4-bis[N-(1-naphthyl)-N-phenyl-amino] biphenyl(NPB)/MoO_3 interface charge transfer mechanism and the present experimental results, we propose a mechanism that mobile carriers generated at the interface and accumulated inside the device change the distribution of electric field inside the device, resulting in an increase of the probability of hole tunneling through the injection barrier from the electrode, which also explains the phenomenon of hole injection enhanced by MoO_3/NPB/Al composite anode. Based on this mechanism, different organic materials other than NPB were applied to form the composite electrode with MoO_3. Similar current enhancement effects are also observed.     

Electron emission studies of CNTs grown on Ti and Ni containing amorphous carbon nanocomposite films

Carbon nanotubes (CNTs) were grown successfully on the as-deposited dual metal (Ti and Ni) embedded films using a radio frequency plasma-enhanced chemical vapor deposition system. The microstructure of CNTs grown on the dual metal films proved to be heavily dependent on the percentages of metals included, varying both in size and in density. Electron emission tests carried out on the films with CNTs grown showed that the threshold field was dependent on the surface morphology of the CNTs, with the lowest threshold field at 3.5 V/μm from 2.5% Ti/Ni film with CNTs. The field enhancement factor, β, of the emitting tips was also calculated from the Fowler–Nordheim plots, where CNTs from the 2.5% Ti/Ni film gave the highest field enhancement factor. However, it was observed that films with a single metal of either Ti or Ni did not manage to grow CNTs, possibly due to a lack of catalyst centres at the surface of the films. It was believed that the Ni nanoclusters acted as catalysts centres giving a rather uniform but randomly orientated type of CNTs. Results obtained pointed that the fabricated nanocomposite material could be a possible choice for cold cathode emitters and the Ti/Ni mixture could be an effective composite for controlling the CNT density.     

Ni/Au层对碳纳米管薄膜强流脉冲发射稳定性的影响

采用酞菁铁高温裂解法在镀有镍金缓冲层的硅基底上生长了碳纳米管薄膜(Ni/Au-CNT),并采用二极结构在相同的主Marx电压下研究了其强流脉冲发射稳定性.结果表明:在脉冲电压峰值为1.60～1.74 MV(对应的脉冲电场峰值为11.43～12.43 V/μm)时,Ni/Au-CNT薄膜首次发射的电流峰值可达331.2A;Ni/Au层不仅能提高CNT薄膜的强流脉冲发射电流峰值,还能提高其发射稳定性;当冷阴极重复脉冲发射7次时,Ni/Au-CNT的脉冲电流峰值衰减到初值的72％,而Ni-CNT和Si-CNT脉冲电流峰值分别衰减到初值的62％和32％.     

沉积工艺参数对碳纳米管薄膜场发射性能的影响

利用微波等离子体化学气相沉积(MWPCVD)方法,在不锈钢衬底上直接沉积碳纳米管膜。通过SEM、拉曼光谱和XRD表征,讨论了制备温度和甲烷浓度对碳纳米管膜场发射的影响。结果表明:不同条件下制备的碳纳米管膜的场发射性能有很大差异,保持氢气的流量(100sccm)、生长时间(10min)、反应室压力不变,当甲烷流量为8sccm、温度为700~800℃时,场发射性能最好,开启场强仅为0.8V/μm,发射点分布密集、均匀。     

Titanium buffer layer for improved field emission of CNT based cold cathode

Carbon nanotube (CNT) based cold cathodes are considered to be the most promising material for fabrication of next generation high-performance flat panel displays and vacuum microelectronic devices. Adhesion of CNTs with the substrate and the contact resistance between them are two of the important issues to be addressed in CNT based field emission (FE) devices. Here in this work, a buffer layer of titanium (Ti) is deposited prior to the catalyst deposition and the growth was carried out using chemical vapor deposition (CVD) technique. There was significant increase in emission current density from 10 mA/cm² to 30 mA/cm² at the field of 4 V/μm by the use of titanium buffer layer due to much less dense growth of CNTs of smaller diameter. Field emission results suggest that the adhesion of the CNTs to the substrate has improved. The titanium buffer layer has also lowered the contact resistance between the CNTs and the substrate because of which a stable emission of 30 mA for a longer duration was obtained.