大电流碳纳米管场发射阴极研究

报道了在较大发射面积上获得较大场发射电流的碳纳米管场发射阴极。为了加强场发射电流,在丝网印刷浆料中增加一种金属纳米颗粒,金属颗粒增强了碳纳米管发射体和衬底的接触,提高碳纳米管和衬底的粘附作用。利用改进后的丝网印刷方法制备了大电流碳纳米管场发射阴极,测得最大发射电流为68.0 mA,阴极有效发射面积约1.1 mm2,发射电流密度约6.2 A/cm2;并成功将改进方法制备的大电流场发射碳纳米管阴极应用于场发射真空器件原型。实验证明这种具有较大发射电流和较大发射电流密度的场发射能够满足部分大功率电子器件的需求。收稿日期:; 修订日期:     

后处理工艺对钛基纳米金刚石涂层场发射特性的影响

采用胶带粘贴、金相砂纸摩擦、射频氢等离子体工艺对钛基纳米金刚石涂层进行了处理,分析了它们对样品的微观表征、场发射性能、发光效果的影响。首先通过电泳法将金刚石粉末移植到金属钛片上,然后经过真空热处理、表面后处理工艺形成了场发射阴极涂层,最后对样品进行了微观表征、场发射特性与发光测试。结果表明,胶带处理在场强达到10 V/μm时,场发射电流密度从50μA/cm~2增j加到72μA/cm~2;金相砂纸处理在10 V/μm场强下的场发射电流由48μA/cm~2提高到82μA/cm~2;适当的氢等离子体处理有助于降低表面功函数,使得金刚石表面的悬键被氢原子饱和,在其表面形成C—H键,进一步降低了电子亲和势,从而提高了样品的场发射性能和发光均匀性。     

碳纳米管/硅纳米孔柱阵列的场发射性能

"通过热化学气相沉积的方法将碳纳米管生长到硅纳米孔柱阵列衬底上．采用场发射扫描电子显微镜、透射电子显微镜、高分辨透射电子显微镜、拉曼光谱和X射线能谱对所制备的样品形貌、组成进行了分析．结果发现：所制备产物为一种具有面积大、准周期性的碳纳米管/硅巢状阵列复合结构．能谱分析表明碳纳米管仅含有碳元素．对样品进行场发射性能测试表明该结构开启电压为1.3 MV/m,当外加电压为4.26 MV/m,发射电流为5 mA/cm2．由FN公式计算相应的场增强因子约为1.1￡104．碳纳米管/硅纳米孔柱阵列好的场发射性能被归     

碳纳米管阴极的短脉冲爆炸场发射与等离子体膨胀

采用碳纳米管制备了一种强流电子束发射阴极,并对碳纳米管阴极在双脉冲条件下的强流发射性能进行了研究.在双脉冲条件下获得了245 A/cm²的强发射电流密度,阴极的开启时间约为40 ns.采用高速分幅相机和CCD相机对强流电子束在空间和时间的分布进行了研究.研究表明连续脉冲实验时,离子体及其膨胀对发射电子束的强度和分布影响很大,双脉冲时脉冲间隔时间内等离子体的膨胀速率约为8.17 cm/μs.等离子体形成时没有优先位置,电子束发射的局部增强位置是随机的.结果表明碳纳米管阴极可以作为强流阴 关键词： 碳纳米管 爆炸场发射 等离子体膨胀 强流电子束     

碳纳米管场发射显示器的研究进展

碳纳米管因具有良好的电子发射特性而成为理想的场发射阴极材料,利用碳纳米管作阴极的场致发射平板显示器件的研究是目前显示技术领域的研究热点之一。报道了场发射显示器（FED）的结构及工作原理、阴极发射材料应具有的特点及碳纳米管在场发射领域中的应用情况。详细地论述了碳纳米管的场致发射特性,包括开启电场、发射电流密度、电流稳定性及发射点密度等,对国内外碳纳米管场发射显示器的发展现状及趋势作了回顾和展望,并对目前所面临的主要问题作了分析,同时提出了一些改进的思路。     

激光烧蚀对碳纳米管薄膜场发射性能的影响

采用丝网印刷工艺制作了碳纳米管(CNTs)薄膜阴极.经适当能量激光烧蚀后,相互粘连的CNTs随表面粘附有机物的蒸发而分散开,管间隙增加、屏蔽效应减小,使得场发射性能大幅度提高,开启场强降低、场倍增因子β增大.Raman光谱分析表明,随激光能量增加,CNTs表面缺陷增多,成为新的场发射点,对其β增大的贡献加强.相对于两电极结构,三电极中平栅极结构场发射性能经激光烧蚀有更显著的改善.这说明激光烧蚀是提高CNTs场发射性能的有效方法. 关键词： 碳纳米管薄膜 场发射 激光烧蚀 Raman光谱     

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。     

丝网印刷制备碳纳米管阴极的强流脉冲发射特性研究

采用丝网印刷法制备了一种大面积的碳纳米管阴极,表征了阴极表面碳纳米管的形貌及分布.研究了该阴极在不同脉冲条件下的高压脉冲发射特性,分析了发射时阴极面等离子体产生和发射点的分布.研究表明：碳纳米管阴极的脉冲发射机制为爆炸电子发射,在平均场强为16.7V/μm的单脉冲电场下,阴极的最高发射电流密度为99 A/cm².在平均场强为15.4 V/μm的双脉冲电场下,阴极的最高发射电流密度为267 A/cm².碳纳米管阴极可以作为强流电子束源在高能微波器件中得到应用. 关键词： 强流脉冲电子束 碳纳米管 阴极 丝网印刷     

新型氧化铝模板自组装制备非晶碳纳米点阵列膜及其场发射性能研究

通过对阳极氧化铝(AAO)模板进行特殊扩孔处理,消除了AAO模板中带电阴离子对沉积碳离子的不良影响,利用磁过滤阴极弧等离子体沉积技术成功制备了非晶碳纳米尖点阵列膜.场发射扫描电镜(FESEM)分析表明,经过氧化和扩孔多步处理制备的AAO模板具有特殊的开口结构,制备的非晶碳纳米尖点阵列完整地复制了AAO模板的孔道阵列结构,纳米点排列整齐有序,直径约100nm,密度达1010cm-2,样品的场发射测试显示,非晶碳纳米点阵列具有良好的电子发射性能,发射电流为10mA/cm-2时的阈值电场为3.7V/μm.     

类富勒烯纳米晶CNx薄膜及其场致电子发射特性

利用微波等离子体增强化学气相沉积技术制备出了CNx薄膜,并利用x射线光电子能谱、x射线衍射、扫描电子显微镜和Raman光谱等测试手段对所制备的CNx薄膜的微结构和成分进行了分析.研究了其场致电子发射特性.发现薄膜的结构和场发射特性与反应系中的甲烷、氮气及氢气的流量比有关,当甲烷、氢气及氮气流量比为8/50/50sccm时,制备的薄膜具有弯曲层状的纳米石墨晶体结构(类富勒烯结构)和很好的场发射特性.场发射阈值电场降低至1.1V/μm.当电场为5.9V/μm时,平均电流密度达70μA/cm2,发射点密度大于1×104cm-2.     

Investigating carbon materials for use as the electron emission source in a parallel electron-beam lithography system

A microelectronic parallel electron-beam lithography system using an array of field emitting microguns is currently being developed. This paper investigates the suitability of various carbon based materials for the electron source in this device, namely tetrahedrally bonded amorphous carbon (ta-C), nanoclustered carbon and carbon nanotubes.Ta-C was most easily integrated into a gated field emitter structure and various methods, such as plasma and heavy ion irradiation, were used to induce emission sites in the ta-C. However, the creation of such emission sites at desired locations appeared to be difficult/random in nature and thus the material was unsuitable for this application. In contrast, nanoclustered carbon material readily field emits with a high site density but the by-products from the deposition process create integration issues when using the material in a microelectronic gated structure.Carbon nanotubes are currently the most promising candidate for use as the emission source. We have developed a high yield and clean (amorphous carbon by-product free) PECVD process to deposit single free standing nanotubes at desired locations with exceptional uniformity in terms of nanotube height and diameter. Field emission from an array of nanotubes was also obtained.     

Characterization of fullerenes and carbon nanoparticles generated with a laser-furnace technique

The microstructure and field emission properties of films prepared from commercial powders of single-wall and multi-wall carbon nanotube films were investigated. In addition to nanotubes, these materials contained amorphous and crystalline carbon phases, and the single-wall powder also contained nano-particles of the Fe-Co catalysts. The turn-on fields were measured to be 2.3 V 7m^-1 for films prepared with the material containing single-wall nanotubes and 2.6 V 7m^-1 for those with multi-wall nanotubes. Long-term stability of emission current for these films was also investigated and correlated to their microstructure. Single-wall material showed a decrease in emission current that extended over several days and that was related to permanent degradation of emission sites. Emission current from the multi-wall material stabilized after an initial increase.     

Vertically aligned carbon nanotubes from natural precursors by spray pyrolysis method and their field electron emission properties

Vertically aligned carbon nanotubes have been synthesized from botanical hydrocarbons: Turpentine oil and Eucalyptus oil on Si(100) substrate using Fe catalyst by simple spray pyrolysis method at 700°C and at atmospheric pressure. The as-grown carbon nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Raman spectroscopy. It was observed that nanotubes grown from turpentine oil have better degree of graphitization and field emission performance than eucalyptus oil grown carbon nanotubes. The turpentine oil and eucalyptus oil grown carbon nanotubes indicated that the turn-on field of about 1.7 and 1.93 V/μm, respectively, at 10 μA/cm². The threshold field was observed to be about 2.13 and 2.9 V/μm at 1 mA/cm² of nanotubes grown from turpentine oil and eucalyptus oil respectively. Moreover, turpentine oil grown carbon nanotubes show higher current density in relative to eucalyptus oil grown carbon nanotubes. The maximum current density of 15.3 mA/cm² was obtained for ∼3 V/μm corresponding to the nanotubes grown from turpentine oil. The improved field emission performance was attributed to the enhanced crystallinity, fewer defects, and greater length of turpentine oil grown carbon nanotubes.     

碳纳米管/金刚石复合材料的场发射特性

采用微波烧结方法制备了碳纳米管/金刚石复合材料。将碳纳米管和纳米金刚石粉末混合后研磨压片,然后在微波等离子气相沉积系统中采用微波烧结。利用扫描电镜对复合材料的表面形貌和微观结构进行了分析,结果显示碳纳米管比较均匀地分散于复合材料中,并在表面形成了发射微尖。利用二极管结构在动态真空室中对复合材料的场发射特性进行了研究,复合材料有较好的场发射特性,电流密度接近15mA/cm2。     

Low-voltage nonstationary electron emission from single-walled carbon nanotubes as exoelectron emission

Low-voltage nonstationary electron emission from single-walled carbon nanotubes after the passage of high autoemission current has been observed. This emission is assumed to be exoelectron emission associated with mechanical stresses and defects appearing in nanotubes due to electrostatic forces acting on nanotubes in a strong electric field.     

纳米碳管的制备及其场发射性能研究

将Ni(NO3)2-Mg(NO3)2体系作为催化剂前驱体,在不同气源比例下用CVD催化裂解法制备纳米碳管,用SEM、TEM和喇曼光谱对其进行了表征和分析,制备出完整性好的纳米碳管.再用两种工艺和配方制备其场发射阴极,对阴极样品进行了场发射性能测试.结果表明,经过氢处理在Si基上制备的CNT阴极发光效果好,且具有良好的场发射性能.     

Effects of microwave plasma treatment on the field emission properties of printed carbon nanotubes/Ag nano-particles films

The effects of Ar microwave plasma treatment on field emission properties of the printed carbon nanotubes (CNTs) cathode films using Ag nano-particles as binder were investigated. The field emission J-E characteristics were measured at varied plasma treatment time. Significant improvement in emission current density, emission stability and uniformity were achieved for the Ar treated CNTs films, even though the plasma treatment increased the turn on electric field slightly. High-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy revealed the microstructural changes of CNTs after the plasma treatment. The improved field emission properties of CNTs film can be attributed to the generation of a high density of structural defects after treatment, which increased greatly the possible emission active sites. Besides, the formation of the sharpened and open-ended CNTs tips is all helpful for improving the field emission properties of the treated CNTs.     

High-field electron emission of carbon nanotubes grown on carbon fibers

Carbon nanotubes with uniform density were synthesized on carbon fiber substrate by the floating catalyst method. The morphology and microstructure were characterized by scanning electron microscopy and Raman spectroscopy. The results of field emission showed that the emission current density of carbon nanotubes/carbon fibers was 10 μA/cm² and 1 mA/cm² at the field of 1.25 and 2.25 V/μm, respectively, and the emission current density could be 10 and 81.2 mA/cm² with the field of 4.5 and 7 V/μm, respectively. Using uniform and sparse density distribution of carbon nanotubes on carbon fiber substrate, the tip predominance of carbon nanotubes can be exerted, and simultaneously the effect of screening between adjacent carbon nanotubes on field emission performance can also be effectively decreased. Therefore, the carbon nanotubes/carbon fibers composite should be a good candidate for a cold cathode material.     

Improved emission uniformity and stability of printed carbon nanotubes in electrolyte

In this paper, we studied the effect of NaCl electrolyte as a surface treatment on improving the uniformity and stability of field emission of screen-printed carbon nanotubes (CNTs). A short period of the electrolyte treatment of CNT films remarkably increase emission uniformity and stability. Furthermore, the field emission characteristics of screen-printed carbon nanotubes (CNTs) such as low turn-on field, high emission current density and strong adhesion of the CNT film on the substrate were also reinforced after post-treated. SEM, TEM and Raman spectrum study revealed that uniformity and stability of field emission is enhanced by two factors. Firstly, the electrolyte treatment appeared to render the CNT surfaces more actively by exposing more CNTs form the CNT paste, which dominates initial uniformity and stability of field emission. Secondly, the number of opened CNTs and defects CNTs of CNT film were increased by electrical current energy.