氮掺杂碳纳米管及其垂直阵列的可控制备研究

IMR OpenIR

	氮掺杂碳纳米管及其垂直阵列的可控制备研究
	宋曼
学位类型	硕士
导师	刘畅
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料学
关键词	碳纳米管氮掺杂异质结构阵列化学气相沉积法可控制备 Carbon Nanotubes Nitrogen Doping Intramolecular Junction Array Chemicalvapor Deposition Controllable Synthesis
其他摘要	" 单壁碳纳米管（SWCNT）根据构成其石墨烯片层的卷曲方式不同，可表现为金属性或半导体性。半导体性SWCNT可用于构建场效应晶体管和光电子器件，而金属性SWCNT可用作高频装置或器件间的互连导线；因而SWCNT被认为是构建下一代纳电子器件的理想材料之一。然而SWCNT离广泛商业化应用仍有相当距离，究其原因，主要是目前还没有一种制备方法能够完全控制单壁碳纳米管的精细结构。虽然半导体性SWCNT的控制制备及选择性后期分离已有很大进展，但制备活性较高的金属性SWCNT的报道相对较少。通过异类原子掺杂实现调控SWCNT的结构和导电属性被认为是非常有前途的一种方法，更是一个挑战。本论文利用氮和碳元素原子尺寸相近可以在引起碳纳米管变形较小的情况下改变其电子结构的特点，以碳纳米管在电子器件方面的应用为目标，重点开展了浮动催化剂化学气相沉积法 (FCCVD) 制备氮掺杂单壁碳纳米管 (N-SWCNT) 以及化学气相沉积法 (CVD) 制备碳纳米管异质结垂直阵列 (CNTIJA)的工作，取得的主要结果如下：以二茂铁、甲烷和三聚氰胺分别作为催化剂、碳源和氮源，采用浮动催化剂化学气相沉积法制备出低掺杂量（<0.1 at.%）的N-SWCNT，通过掺杂量和掺杂形式的控制，实现了金属性富集SWCNT的可控制备，并对掺杂前后SWCNT的结构进行系统的表征和分析，研究表明：氮在SWCNT网格上的掺杂会促进金属性SWCNT的形成，然而吡啶型掺杂会在管壁中引入缺陷、抑制大直径SWCNT的生长，导致掺杂后的SWCNT的结晶性和热稳定性有所下降。通过进一步优化制备条件，实现了氮原子在SWCNT石墨网格上的直接取代掺杂，获得了高质量的N-SWCNT，其抗氧化温度高达880 ºC。表明：改进浮动催化剂化学气相沉积法可以通过氮掺杂在不改变SWCNT结晶性的同时来调控其电子结构。为大量可控制备高质量、结构均一、金属性SWCNT打下了基础。采用离子束辅助沉积法将Al2O3阻挡层和Fe催化剂分别均匀得溅射到SiO2/Si基体上，以乙烯和乙腈分别作为碳源和氮源制备CNT/N-CNT异质结垂直阵列。SEM和TEM观察表明：异质结部分有明显的过渡区域，XPS表征表明：异质结氮掺杂碳纳米管一侧的氮掺杂量为0.1-0.7 at.%。通过调控乙腈的反应量和反应时间可控制异质结的位置、结构、个数和氮掺杂量，进而实现具有异质结结构的碳纳米管垂直阵列的可控制备。为碳纳米管异质结构垂直阵列在二极管、纳米开关、放大器等领域的应用奠定了基础。"; " Single-walled carbon nanotubes (SWCNTs) can be either metallic or semiconducting, depending on how a graphene sheet is rolled up. Semiconducting tubes can be used in field effect transistors (FETs) and optoelectronic devices, and metallic tubes may find applications in high-frequency devices and interconnections of nanodevices. Thus, CNTs are considered as a promising candidate for assembling next generation electronic devices. However, it remains a great challenge to realize these above applications. The main obstacle is to obtain CNT samples with uniform structure and properties. For now, most of the as-prepared CNT samples are mixture of semiconducting and metallic tubes. One of the proposed solutions for this issue is to tailor the electronic structure of CNTs by doping with heteroatoms. In this thesis, we focus on the controllable synthesis of nitrogen-doped SWCNTs and vertically aligned CNT/N-doped CNT arrays with intramolecular junctions. The main results obtained are as follows: N-doped SWCNTs (N-SWCNTs) with low nitrogen content were synthesized using an ambient pressure floating catalyst chemical vapor deposition method (FCCVD). Ferrocene, methane, and melamine were used as catalyst, carbon source, and nitrogen source, respectively. Characterizations of TG, TEM, and laser Raman spectroscopy showed that the N-SWCNTs kept an intact structure although their crystalization and chemical stability decrease slightly compared to pristine SWCNTs. We attribute the phenomina to the defects resulted from nitrogen incorporation. As previously reported, nitrogen doping improves the electronical density of state (DOS) in the Fermi level of SWCNTs. Here, we construct field effect transistors (FETs) using the as-grown N-SWCNTs. The measurement results revealed that our N-SWCNTs are metallic enriched tubes predominant. By further tuning the growth conditions, we obtained high quality N-SWCNTs with a high oxidation resistance temperature of 880 ºC. The fabrication of CNT intramolecular junctions in a controllable way is a great challenge. Here we use a simple CVD method to synthesize vertically aligned undoped/N-doped CNT intramolecular junction arrays (CNTIJA). Fe, C2H4, and CH3CN were used as catalyst, carbon source, and nitrogen source, respectively. SEM and TEM observations revealed that there exsits an obvious transition area near the junction. XPS characterization shows that the nitrogen content of the N-doped CNT can be tuned in the range of 0.1-0.7 at.%. The position, structure, and numbers of CNT intramolecular junctions can be controlled by tuning relative growth conditions. "
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64527
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	宋曼. 氮掺杂碳纳米管及其垂直阵列的可控制备研究[D]. 北京. 中国科学院金属研究所,2012.