石墨基底上垂直生长碳纳米管为芯的碳锥结构

采用一种改进的化学气相沉积方法，成功地在石墨基底上自组装生长出以碳锥为支撑的、碳纳米管为芯的新型功能材料.该结构的材料可以用作扫描电子显微镜探针和场发射电子显微镜的针尖.利用电子显微镜研究了不同合成条件对该碳纳米管与碳锥结构生长的影响，给出了最优生长条件，并讨论了生长机制. 关键词： 碳锥 碳纳米管 化学气相沉积 场发射     

InN纳米线的低压化学气相沉积及其场发射特性研究

利用低压化学气相沉积方法在以Au作催化剂的Si衬底上生长了InN纳米线. 扫描电子显微镜分析表明，这些纳米线的直径在60—100 nm的范围内, 而其长度大于1 μm.高分辨透射电子显微镜图像表明，合成的纳米线中含有六方相和立方相的InN晶体.这些InN纳米线具有良好的场发射特性和稳定的场发射电流，其开启场为10.02 V/μm(电流密度为10 μA/cm²)，在24 V/μm 的电场下，其电流密度达到5.5 mA/cm².此外，对InN纳米线的场发射机理也进行了讨论. 关键词： InN纳米线 场电子发射 非线性Fower-Nordheim曲线     

等离子体增强热丝CVD生长碳纳米尖端的研究

用CH₄，NH₃和H₂为反应气体，利用等离子体增强热丝化学气相沉积系统在不同偏压电流的条件下制备了碳纳米尖端，并用扫描电子显微镜和显微Raman光谱仪对碳纳米尖端进行了研究.结果表明碳纳米尖端是石墨结构，随着偏压电流的增大，碳纳米尖端的顶角减小，生长速率增大.结合有关等离子体和溅射的理论，分析讨论了碳纳米尖端的形成和碳纳米尖端的生长随偏压电流的变化. 关键词： 碳纳米尖端 等离子体 化学气相沉积     

光电子技术与器件 其他

O462．4 2006065340一种有效提高CNTs/CNFs阴极场发射性能的热处理方法=A heat-treatment process for effectively enhancing field emission characteristics of CNTs/CNFs cathodes[刊,中]/郭平生(华东师范大学物理系功能纳米材料和器件应用研究中心,上海(200062)),孙卓…//光电子·激光．—2006,17(6)．—681-684报道了一种新的提高碳纳米管/碳纳米纤维(CNTs/ CNFs)丝网印刷阴极场发射性能的后处理方法。利用化学汽相沉积(CVD)方法制备的CNTs/CNFs作为阴极材料,采用丝网印刷工艺在玻璃基板上制备场发射阴极,在Hz和C_2 H_2混合气氛下500℃处理20 min,能有效提高其场发射性能,改善场发射显示器的发光均匀性。热处理后     

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     

利用微波等离子体增强化学气相沉积法定向生长纳米碳管的研究

利用微波等离子体增强化学气相沉积法在氢气和甲烷的混合气体中定向生长纳米碳管.经扫描电子显微镜观察与分析，发现纳米碳管在与基板垂直的方向上整齐排列，管径较均匀且长度基本相同. 关键词： 微波等离子体 纳米碳管     

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CN_x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CN_x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8/50/50 sccm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 关键词： 类富勒烯 x薄膜')" href="#">CN_x薄膜 场致电子发射 微波等离子体增强化学气相沉积     

白碳纳米晶薄膜及其场致电子发射特性

利用微波等离子体化学气相沉积方法,以甲烷、氢混合气体为反应气体,具有钛镀层的玻璃作为衬底,制备了具有sp¹杂化结构的白碳纳米晶薄膜。利用X射线衍射、俄歇电子能谱,以及扫描电子显微镜对薄膜结构进行了表征。以白碳纳米晶薄膜为阴极,以镀有ITO透明导电薄膜玻璃为阳极,采用二极管结构,测试了白碳纳米晶薄膜的场致电子发射特性。开启电场为2.5 V/μm,在电场为5 V/μm时的电流密度为200μA/cm²。对白碳纳米晶薄膜生长机理,以及其场致电子发射机制进行了讨论。     

在双热舟化学气相沉积系统中通过掺In技术生长GaN纳米线和纳米锥

在现有的一台蒸发镀膜机基础上，设计加工了一个双热舟化学气相沉积系统.该系统具有真空度高、升温速度快、源和衬底温度可分别控制等优点，有利于化合物半导体纳米材料的生长.利用该生长系统，通过在生长过程中掺入等电子杂质In作为表面活性剂，分别在Si衬底和3C-SiC/Si衬底上生长出高质量的具有纤锌矿结构的单晶GaN纳米线和纳米尖三棱锥.所得产物通过场发射扫描电子显微镜、高分辨透射电子显微镜、能量色散x射线谱仪、x射线衍射仪，和荧光谱仪进行表征.这里所用的生长方法新颖，生长出的GaN纳米尖三棱锥在场发射和激光方面有潜在的应用价值. 关键词： GaN 纳米结构 透射电子显微镜 光致荧光谱     

衬底对化学气相沉积法制备氧化硅纳米线的影响

通过化学气相沉积法在不同衬底上制备了大量的氧化硅纳米线.选用衬底为Si片、带有约100nm厚SiO2氧化层Si片和石英片.利用场发射扫描电子显微镜(SEM)和透射电镜(TEM，配备有能谱仪)对样品的表面形貌、结构和成分进行研究.结果表明：这些纳米线都为非晶态，但在不同衬底上生长的纳米线形貌、尺寸和化学成分不同.讨论了各种衬底对不同特征氧化硅纳米线生长的影响. 关键词： 化学气相沉积 纳米线 纳米颗粒     

Effect of temperature on the electron field emission from aligned carbon nanofibers and multiwalled carbon nanotubes

Effect of temperature and aspect ratio on the field emission properties of vertically aligned carbon nanofiber and multiwalled carbon nanotube thin films were studied in detail. Carbon nanofibers and multiwalled carbon nanotube have been synthesized on Si substrates via direct current plasma enhanced chemical vapor deposition technique. Surface morphologies of the films have been studied by a scanning electron microscope, transmission electron microscope and an atomic force microscope. It is found that the threshold field and the emission current density are dependent on the ambient temperature as well as on the aspect ratio of the carbon nanostructure. The threshold field for carbon nanofibers was found to decrease from 5.1 to 2.6 V/μm when the temperature was raised from 300 to 650 K, whereas for MWCNTs it was found to decrease from 4.0 to 1.4 V/μm. This dependence was due to the change in work function of the nanofibers and nanotubes with temperature. The field enhancement factor, current density and the dependence of the effective work function with temperature and with aspect ratio were calculated and we have tried to explain the emission mechanism.     

Improving the field-emission properties of carbon nanotubes by magnetically controlled nickel-electroplating treatment

A novel magnetically controlled Ni-plating method has been developed to improve the field-emission properties of carbon nanotubes (CNTs). The effect of the magnetic field and Ni-electroplating on CNT field-emission properties was investigated, and the results are demonstrated using scanning electron microscopy, J-E and the duration test. After treatment, the turn-on electric field declines from 1.55 to 0.91 V/μm at an emission current density of 100 μA/cm², and the emission current density increases from 0.011 to 0.34 mA/cm² at an electric field of 1.0 V/μm. Both the brightness and uniformity of the CNT emission performance are improved after treatment.     

Morphology and temperature-dependent electron field emission from vertically aligned carbon nanofibers

Effects of temperature and the aspect ratio on the electron field emission properties of vertically aligned carbon nanofibers in thin-film form were studied in detail. Vertically aligned carbon nanofibers have been synthesized on silicon substrates via a direct current plasma enhanced chemical vapor deposition technique. Surface morphologies of the films were studied by an atomic force microscope. It was found that the length of the nanofibers increased and the diameter decreased as the thickness of the Ni catalyst film decreased. The threshold field for the electron field emission was found to be in the range from 4.3 to 5.4 V/μm for carbon nanofibers having different aspect ratios. The threshold field for carbon nanofibers having diameter ∼ 200 nm and aspect ratio ∼7.5 was found to decrease from 4.8 to 2.1 V/μm when the temperature was raised from 27 to 350 °C. This dependence was due to the change in work function of the nanofibers with temperature. The field enhancement factor, the current density and the effective work function were calculated and used to explain the emission mechanism. PACS 81.07.De; 61.10.-i; 79.70.+q; 73.30.+y     

The enhanced field-emission properties of screen-printed single-wall carbon-nanotube film by electrostatic field

In this work, we improved the field-emission properties of a screen-printed single-wall carbon-nanotube (SWCNT) film by applying a strong electrostatic field during the drying process after the printing. By applying the strong field, more tips of SWCNTs could emerge from the screen-printed film and turn somewhat toward the erecting direction because of the repulsive force among the SWCNTs. The field-emission properties of the film were thus improved obviously. The improved field emitters sample has low electron emission turn-on field (E_to = 1.22 V/μm), low electron emission threshold field (E_th = 2.32 V/μm) and high brightness with good uniformity and stability. The lowest operating field of the improved sample is below 1.0 V/μm and its optimum current density exceeds 3.5 mA/cm².     

Morphological effects on the field emission characteristics of zinc oxide nanotetrapods films

The direct growth of a tetrapod-like ZnO nanostructure has been accomplished by using a thermal oxidation method without any catalysts. Studies on the field emission properties of the ordered ZnO nanotetrapods films found that the shape of the ZnO nanotetrapods has considerable effect on their field emission properties, especially the turn-on field and the emission current density. Compared with the rod-like legs ZnO nanotetrapods, the nanotetrapods with acicular legs have a lower turn-on field of 2.7 V/μm at a current density of 10 μA/cm², a high field enhancement factor of 1830, and an available stability. More importantly, the emission current density reached 1 mA/cm² at a field of 4.8 V/μm without showing saturation. The results could be valuable for using the ZnO nanostructure as a cold-cathode field-emission material.      

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     

CNx纳米管的制备、结构观察及低场致电子发射性能研究

采用高温热解法，以乙二胺为前驱液，在沉积有铁催化剂的p型硅（111）基底上制备出了定向生长的CNx纳米管.利用扫描电子显微镜、高分辨率透射电子显微镜和拉曼光谱对CNx纳米管进行了形貌观察和表征.CNx纳米管的高度在20?μm左右，直径在50—100nm之间，具有明显的“竹节状”结构，结晶有序度较差.对CNx纳米管薄膜进行低场致发射性能测试：外加电场为1.4V/μm，观察到20?μA /cm2发射电流，外电场升至2.54V/μm时发射电流达到1.280mA/cm2，在较高外电场下，没有发现电流“饱和”.这比 关键词： CNx纳米管 高温热解 “竹节状”结构 场致发射     

ZnO纳米棒的低温溶液法制备、光电特性研究及其在有机/无机复合电致发光中的应用

利用水热法制备了垂直于衬底的定向生长的ZnO纳米棒,利用扫描电子显微镜及光致发光的方法对其形貌及光学特性进行了表征,利用场发射性能测试装置对ZnO纳米棒的场发射性能进行了测试.结果表明:利用水热法在较低的温度(95 ℃) 下生长了具有较好形貌和结构的ZnO纳米棒,并表现出了较好的场发射特性,当电流密度为1 μA/cm²时,开启电场是2.8 V/μm,当电场为6.4 V/μm时,电流密度可以达到0.67 mA/cm²,场增强因子为3360.稳定性测试表明,在5 h内,4.5 V/μm的电场下,其波动不超过25%.将制备的ZnO纳米棒应用到有机/无机电致发光中,其中ZnO纳米棒为电子传输层,m-MTDATA(4,4',4″-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine) 为空穴传输层,得到了ZnO的342 nm的紫外电致发光,此发光较ZnO纳米棒光致发光的紫外发射有约40 nm的蓝移. 关键词： ZnO纳米棒 场发射 水热法 有机/无机复合电致发光     

Synthesis of Cu-ZnO and C-ZnO nanoneedle arrays on zinc foil by low temperature oxidation route: Effect of buffer layers on growth, optical and field emission properties

Different densities of ZnO nanoneedle films have been prepared by pre-coated zinc foils with thin layer of copper and carbon followed by thermal oxidation at 400 °C in air. The X-ray diffraction patterns show well defined peaks, which could be indexed to the wurtzite hexagonal phase of ZnO. The scanning electron microscope images clearly reveal formation of ZnO needles on the entire substrate surface. The X-ray photoelectron spectroscopy studies indicate that Cu and C ions are incorporated into the ZnO lattice. Photoluminescence studies evaluate different emission bands originated from different defect mechanism. From the field emission studies, the threshold field, required to draw emission current density of ∼100 μA/cm², is observed to be 2.25 V/μm and 1.57 V/μm for annealed zinc foil pre-coated with copper and carbon, respectively. The annealed film with copper layer exhibits good emission current stability at the pre-set value of ∼100 μA over a duration of 4 h. The results show that buffer layer is an important factor to control the growth rate, resulting in different density of ZnO needles, which leads to field emission properties. This method may have potential in fabrication of electron sources for high current density applications.