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采用等离子体增强热灯丝化学气相沉积方法,以甲烷和氢气为反应气体,在钨丝衬底上制备出准直的碳纳米纤维(CNFs),其生长密度小于10.6cm-2,长度为6—30μm,直径为60—100nm.并采用自制的双探针扫描电子显微镜系统,对所生长的单根CNF作了场发射特性研究.结果表明,其场发射开启电压约为5V/μm,相应的发射电流达到20μA/cm2,同时,对不同长度的CNFs及单根CNF不同位置的场发射研究表明,场发射电流的大小不仅与材料本身的功函数、外电场场强、材料的微观结构以及宏观的几何结构有关,而且电子在输运过程中所受到的散射也是决定场发射电流大小的关键因素.
关键词:
碳纳米纤维
化学气相沉积
场发射
扫描电子显微镜 相似文献
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"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 相似文献
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以二茂铁和二甲苯分别作为催化剂和碳源,采用一种无模板的化学气相沉积法,使用单温炉设备,成功地制备了高度定向的碳纳米管阵列.分别用扫描电子显微镜、透射电子显微镜和电子能量散射谱、拉曼光谱对碳纳米管阵列进行形貌观察和表征, 并研究了不同工艺参数对碳纳米管阵列形貌的影响.结果表明:在生长温度为800℃,催化剂浓度为0.02g/mL,抛光硅片上容易获得高质量的定向碳纳米管阵列,在此优化条件下生长的定向碳纳米管的平均生长速率可达25μm/min. 相似文献
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LPCVD法制备碳纳米管薄膜及其场发射性能的研究 总被引:3,自引:0,他引:3
采用低压化学气相沉积法(LPCVD)在镍片上直接制备碳纳米管(CNTs)薄膜,系统地研究了生长温度(500~800℃)对碳纳米管薄膜形貌、结构及场发射性能的影响,并对此方法的生长机理进行了分析。当温度从500℃升高到650℃时,碳纳米管的生长速率随着温度升高而增大,而温度继续上升,速率则明显减小。利用扫描电镜(SEM)和拉曼光谱仪表征和检测了碳纳米管薄膜的形貌和结构。碳纳米管的管径、长度、一致性和晶化程度随温度都有明显的变化。同时还对碳纳米管薄膜的场发射特性进行了测试,对其场发射机理进行了深入地探讨,表明温度对碳纳米管的性能有很大影响,并存在最优化的温度条件。实验结果表明碳纳米管薄膜的形貌、结构及其场发射性能可通过生长温度进行一定范围的控制。 相似文献
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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 相似文献
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用射频等离子体辅助化学气相沉积方法生长碳纳米洋葱.电子显微镜观察表明,产物中无碳纳米管等伴随生成,因而制得了较高产率、较高纯度的纳米洋葱.尤其是Co-SiO2催化剂生长的碳纳米洋葱,实心、光滑,且内无催化剂颗粒,其外层由未闭合的、呈波浪状的石墨片构成,显示出与众不同的微观结构和性能.提出了该方法中碳纳米洋葱的生长机理为碳笼由里向外嵌套形成球形粒子.对波浪状、非闭合结构的形成过程进行了讨论.
关键词:
射频等离子体
化学气相沉积
碳纳米洋葱 相似文献
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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 相似文献
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碳纳米管场效应管是未来纳米器件的发展方向,而制造纳米器件的前提是拾取碳纳米管,基于扫描电子显微镜(SEM)的微纳机器人操作系统能够实现碳纳米管拾取操作.本文建立拾取操作中碳纳米管与原子力显微镜(AFM)探针间范德瓦耳斯力力学模型,不同接触状态下范德瓦耳斯力越大越有利于拾取碳纳米管.在SEM视觉反馈图像中建立相对坐标系,首先提出倾角变值方法检测碳纳米管与AFM探针的接触状态,然后运用动态差值方法识别碳纳米管与AFM探针空间位姿并校正碳纳米管位姿,最后自下而上拾取碳纳米管.实验结果表明:拟合直线倾角变值较大时碳纳米管与AFM探针发生接触,动态差值变化为零时碳纳米管与AFM探针为空间线接触,在完全线接触模型下选择合适的接触角度、接触长度和拾取速度能够成功拾取碳纳米管. 相似文献
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Fabrication of ZnO nanoparticles-embedded hydrogenated diamond-like carbon films by electrochemical deposition technique
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ZnO nanoparticles-embedded hydrogenated diamond-like carbon (ZnO-DLC) films have been prepared by electrochemical deposition in ambient conditions. The morphology, composition, and microstructure of the films have been investigated. The results show that the resultant films are hydrogenated diamond-like carbon films embedded with ZnO nanoparticles in wurtzite structure, and the content and size of the ZnO nanoparticles increase with increasing deposition voltage, which are confirmed by X-ray photoelectron spectroscopy (XPS), Raman, and transmission electron microscope (TEM). Furthermore, a possible mechanism used to describe the growth process of ZnO-DLC films by electrochemical deposition is also discussed. 相似文献
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Ultrafine porous carbon fibers (UPCFs) were successfully synthesized by chemical activation of electrospun polyacrylonitrile fibers. In the current approach, potassium hydroxide was adopted as activation reagent. UPCFs were systematically evaluated by scanning electron microscope and nitrogen adsorption. The mass ratio of potassium hydroxide to preoxidized fibers, activation temperature and activation time are crucial for producing high quality UPCFs. The relationships between porous structure and process parameters are explored. UPCFs were applied as adsorbent for nitrogen monoxide to be compared with commercial porous carbon fibers. 相似文献
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Femtosecond pump probe spectroscopy is employed to study the photo-induced absorption feature in the single-walled carbon nanotube transient spectrum. The two advantages of the experiment, a chirality enriched sample and tuning the pump wavelength to the resonance of a specific nanotube species, greatly facilitate the identification of the photo-induced absorption signal of one tube species. It is found that a photo-induced absorption feature is located at one radial breathing mode to the blue side of the E11 state. This finding prompts a new explanation for the origin of the photo-induced absorption: the transition from the ground state to a phonon coupled state near the E ii state. The explanation suggests a superposition mechanism of the photo-bleach and photo-induced absorption signals, which may serve as a key to the interpretation of the complex pump probe transient spectrum of carbon nanotubes. The finding sheds some light on the understanding of the complex non-radiative relaxation process and the electronic structure of single-walled carbon nanotubes. 相似文献
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A series of hydrogenated amorphous carbon (a-C:H) films were deposited on silicon substrates by microwave plasma chemical vapor deposition technique with a mixture of hydrogen and acetylene. The effects of flow ratio of hydrogen to acetylene on surface morphology and structure of a-C:H films were investigated using surface-enhanced Raman spectroscopy and scanning probe microscope (SPM) in the tapping AFM mode. Raman data imply a transition from graphite-like phase to diamond-like bonding configurations when the flow ratio increases. AFM measurements show that the increase in hydrogen content, to some extent, can smoothen the surface morphology and decrease the RMS roughness. Excessive hydrogen is found to cause the formation of polymeric hydrocarbon clusters in the films and reduce deposition rate. 相似文献
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