经典的中英文摘要格式写作模式.docx

1、经典的中英文摘要格式写作模式附件6论文中英文摘要格式作者姓名：罗俊论文题目：一维金属/半导体轴向异质结的制备、表征与伏安特性作者简介：罗俊，男，1980年2月出生，2001年9月师从于清华大学朱静教授，于2006年7月获博士学位。中 文 摘 要金属/半导体异质结根据伏安特性的表现分为欧姆接触和肖特基接触两种类型，它们分别是微电子技术中重要的互联单元和功能单元。因此，纳米尺度的金属/半导体异质结的制备、结构和特性是进一步发展微电子技术和纳电子科技的重要研究领域之一。本论文工作结合纳米材料和纳米结构的特点，将发展制备技术、显微结构表征方法、性能测试与一维纳米异质结的研究紧密结合，系统地研究了Ni/

2、MWCNT（多壁碳纳米管）/a-CNT（非晶碳纳米管）、Ag/a-CNT等一维金属/半导体轴向异质结的制备、显微结构和伏安特性，获得一系列创新性研究成果。首先，本文将常用于制备金属纳米线的电化学沉积方法和常用于制备碳纳米管（或硅纳米线）的化学气相沉积（CVD）方法结合起来，以多孔阳极氧化铝（AAO）为模板，开发出一种用于制备一维金属/半导体轴向异质结阵列的普适性方法。其中的AAO模板是一种片状薄膜，内部有贯通上下表面、排列整齐、直径为纳米尺度、长度为微米尺度的孔道。利用这种模板和这种普适性方法，Ni/MWCNT/a-CNT、Ag/a-CNT、Ag/Si和Pt6Si5/Si四种不同种类的一维金属

3、/半导体轴向异质结的整齐阵列已经被成功制备。这些一维异质结的显微结构被用透射电子显微镜（TEM）的高分辨成像技术、选区电子衍射谱、微衍射谱（NBD）和能量色散谱（EDX）进行表征。结果表明，它们都是由各自组成材料的纳米线或纳米管首尾连接而成。其中，Pt6Si5/Si一维异质结的Pt6Si5纳米线部分是由电化学沉积制备的Pt纳米线在CVD过程中转变而来的。这些Pt纳米线是由许多Pt纳米颗粒组成的多晶纳米线。在这些Pt纳米颗粒之间存在着缝隙，使得CVD过程中由SiCl4气体和氢气混合而成的源气体可以渗入到Pt纳米线内部、并和Pt纳米线充分反应、获得单晶Pt6Si5纳米线。继续供给的源气体用于在Pt

4、6Si5纳米线的头部上生长Si纳米线，从而最终形成Pt6Si5/Si一维异质结。金属硅化物是常用于电子工业的金属性材料，这个制备异质结的过程也为制备金属硅化物纳米线提供了一种新方法。根据此种方法，通过调节制备参数，不含Si纳米线的单晶Pt6Si5纳米线已被成功制备。在Ni/MWCNT/a-CNT一维异质结中，MWCNT由Ni纳米线的头部催化生长而成，a-CNT由AAO模板的孔道内壁催化生长而成。这两种生长机制在制备过程中共同作用，控制形成Ni/MWCNT/a-CNT一维异质结的特殊的界面结构：在Ni纳米线和MWCNT之间的界面处，MWCNT的每层管壁都与Ni纳米线的头部相连；在MWCNT和a-

5、CNT之间的界面处，MWCNT的多个外层管壁都与a-CNT相连。这种对界面结构的控制会导致：当Ni纳米线和a-CNT被金属电极连入电学回路时，MWCNT的多个外层管壁能同时参与电路中的电学传输。这是一种特殊的电学传输模式。在表征Ni/MWCNT/a-CNT一维异质结的界面结构的同时，由于MWCNT各管壁的电学性质决定于其螺旋结构，本文工作也用电子衍射谱表征了MWCNT本身的螺旋结构。结果发现有两类异质结，一类异质结中的MWCNT的所有管壁都是金属性的，另一类异质结中的MWCNT既含有金属性管壁、也含有半导体性管壁。但是，在另一方面，高分辨TEM像表明，这两类异质结的MWCNT中都有大量的缺陷存

6、在。这些缺陷会影响MWCNT的电学特性、使它们都表现为半导体特性。本文工作在对MWCNT螺旋结构的表征中还发现，MWCNT侧壁区域的高分辨TEM像中的点阵像不是侧壁区域的结构像、是0002和多束衍射波互相干涉成像的结果；芯部区域的高分辨TEM像及其快速傅立叶变换（FFT）谱反映了所有管壁的螺旋角信息，更有助于螺旋性的判断。Ni/MWCNT/a-CNT一维异质结的特殊的界面结构使得研究其电学性能颇具吸引力。但是，这种异质结由金属Ni纳米线、MWCNT和a-CNT三个部分组成，其结构复杂。如果用金属电极将这种异质结的金属纳米线部分和a-CNT部分连入测量电路，结构就变得更加复杂。因此，本文先从a-

7、CNT着手，通过研究其电阻随温度的变化特性发现它是非晶半导体，再以Ag/a-CNT一维异质结为具体对象来研究金属材料和a-CNT之间的接触的电学性能。具体实验做法是：对于在AAO模板中组成整齐阵列的Ag/a-CNT一维异质结，将其Ag纳米线部分定义为下部，将a-CNT部分定义为上部；部分刻蚀AAO模板的两侧表面，使Ag纳米线部分的根部和a-CNT部分的头部都露出模板之外；在Ag纳米线部分的根部一侧蒸镀上一层金属薄膜，通过此薄膜将Ag纳米线部分的根部连入导电原子力显微镜（AFM）的电路中，再用AFM针尖上的Pt镀层接触a-CNT部分的头部，从而形成一个电学回路、测量异质结的伏安特性。测量结果表明

8、Ag/a-CNT一维异质结有两类，一类表现出线性伏安特性、另一类表现出对称的非线性伏安特性。对这些伏安特性的进一步实验和分析表明，AFM针尖表面上的Pt镀层与a-CNT部分的头部之间的接触是欧姆接触，并且其电阻很小、可以在分析Ag/a-CNT一维异质结的本征伏安特性时忽略；非线性伏安特性的非线性是由相应异质结中的a-CNT导致的，不是由异质结中Ag纳米线和a-CNT之间的接触导致的。这些发现都指明，a-CNT分别和Ag纳米线、AFM针尖表面上的Pt镀层之间的接触都是欧姆接触。能带结构分析表明，这些欧姆接触的欧姆特性来源于非晶半导体能带结构的一般性特点，具有普适性。在此研究的基础上开展对Ni/M

9、WCNT/a-CNT一维异质结的电学性能的研究。先用电子束光刻技术在13个单根Ni/MWCNT/a-CNT一维异质结的两端组装上电极，再通过这些电极测量其伏安特性，发现所有异质结都表现出整流效应。这说明这些异质结中都存在肖特基接触。由于a-CNT和金属材料之间的接触都是欧姆性的，肖特基接触只可能存在于MWCNT的两端或其中一端。这被进一步的实验证实：对其中一些异质结施加过高的电压，导致异质结中被反向偏置的肖特基接触崩溃，实验表现为异质结崩断于某个位置，由此来定性分析肖特基接触的存在和位置。结果发现这些被崩断的异质结中的MWCNT都是半导体性，有的异质结中崩溃的肖特基接触位于Ni纳米线和MWCN

10、T之间的接触位置，其余的异质结中崩溃的肖特基接触位于MWCNT和a-CNT之间的接触位置，这两类异质结崩断时被施加的电压的极性是不一样的。可以同时解释这些定性分析结果的一个假设是，在这些异质结中，MWCNT和Ni纳米线、a-CNT之间的接触都是肖特基接触，并且，它们面对面地串联着。根据这个假设，用介观层次上的热发射理论的公式对所有异质结的伏安特性进行拟合，结果发现，当对肖特基接触的势垒仅仅考虑镜像力的影响（这是肖特基接触在实际中接近理想的状态）时，13个异质结中的25个肖特基接触的伏安特性与公式符合，仅仅1个肖特基接触偏离了考虑镜像力影响的热发射理论公式。这些定性和定量分析表明，所有异质结中的

11、MWCNT都是半导体性，在每个MWCNT的两端各存在一个肖特基接触，这些肖特基接触中的绝大多数符合介观层次上的热发射理论、仅受到镜像力的影响，是实际中接近理想状态的肖特基接触。这种性能优秀的肖特基接触的大量获得，应该归因于它们对应的异质结的特殊结构MWCNT中有多层管壁同时与Ni纳米线和a-CNT接触、因而能同时参与电学传输，这种多层管壁同时参与接触和电学传输的模式保证了电学传输过程中接触的可靠性和对干扰因素的抵抗能力。这些研究和发现为热发射理论应用于一维纳米材料相互之间的肖特基接触做出了有意义的探索和有效的例证。关键词：一维金属/半导体异质结；伏安特性；肖特基接触；欧姆接触；多壁碳纳米管Sy

12、nthesis, Characterization and Current-Voltage Characteristic of One-Dimensional Metal/Semiconductor Axial HeterojunctionsLuo JunABSTRACTMetal/semiconductor heterojunctions are divided into two types, ohmic and Schottky contacts, according to their current-voltage characteristics. The two types are i

13、mportant interconnecting and functional elements, respectively, in microelectronics. Therefore, syntheses, structures and properties of nano-scale metal/semiconductor heterojunctions are one of significant scientific fields for further development of microelectronics and nanoelectronics.In this diss

14、ertation taking into account characteristics of nano-materials and nano-structures, studies on one-dimensional (1D) heterojunctions are integrated with development of synthesis techniques, microstructure characterizations and property measurements. Syntheses, microstructures and current-voltage char

15、acteristics of 1D metal/semiconductor axial heterojunctions, such as Ni/MWCNT (multi-walled carbon nanotube)/a-CNT (amorphous carbon nanotube) and Ag/a-CNT, have been studied systemically. A series of creative results have been obtained.Firstly, a universal method to synthesize ordered arrays of 1D

16、metal/semiconductor axial heterojunctions has been developed by combining electrochemical deposition widely used for synthesizing metal nanowires and chemical vapor deposition (CVD) widely used for carbon nanotubes or Si nanowires with anodic aluminum oxide (AAO) membranes as templates. The AAO temp

17、lates are a kind of sheet membrane containing orderly aligned channels with nano-scale diameters and micro-scale lengths through the whole membranes. Ordered arrays of four types of 1D axial heterojunction, such as Ni/MWCNT/a-CNT, Ag/a-CNT, Ag/Si and Pt6Si5/Si, have been fabricated.The structures of

18、 the heterojunctions have been characterized by high resolution images, selected-area electron diffraction patterns, nano-beam diffraction (NBD) patterns and energy dispersive X-ray (EDX) spectra of transmission electron microscope (TEM). It is shown that all of the heterojunctions consist of the co

19、mponent nanowires/tubes connected end to end. Of the four types of heterojunctions, the Pt6Si5 parts of the Pt6Si5/Si heterojunctions are from Pt nanowires fabricated by electrochemical deposition. The Pt nanowires were polycrystalline and consisted of many Pt nano-particles, among which gaps existe

20、d. The gaps permitted the source gas mixing SiCl4 and H2 of the CVD process to filter into the Pt nanowires, and then the source gas reacted adequately with the Pt nanowires. Consequently, single-crystal Pt6Si5 nanowires were obtained. The supply of the source gas continued for synthesizing Si nanow

21、ires on the tips of the Pt6Si5 nanowires, and the Pt6Si5/Si heterojunctions formed finally. This offers a new method for synthesizing nanowires of metal silicides, which are a kind of metallic materials widely used in the electronic industry. According to this new method, pure Pt6Si5 nanowires witho

22、ut Si nanowires were synthesized successfully by adjusting the synthesis conditions. For the Ni/MWCNT/a-CNT heterojunctions, the MWCNTs were grown by the catalysis of the tips of the Ni nanowires, and the a-CNTs were by the catalysis of the channel walls of the AAO templates. During synthesizing the

23、 Ni/MWCNT/a-CNT heterojunctions, the two growth mechanisms functioned simultaneously and controlled the forming of the unique interfacial structures of the heterojunctions, where each wall of the MWCNT in each heterojunction was in direct contact with the tip of the Ni nanowire at the Ni/MWCNT inter

24、face, and multiple outer walls of the MWCNT were contacted by the a-CNT at the MWCNT/a-CNT interface. This control of the interfacial structures enables that multiple outer walls of a MWCNT can simultaneously participate in electrical transport when the corresponding Ni and the corresponding a-CNT p

25、arts are connected into an electrical circuit by metal electrodes. This is a unique model of electrical transport.In addition to the interfacial structures of the Ni/MWCNT/a-CNT heterojunctions, the helical structures of the MWCNTs in these heterojunctions have been characterized by electron diffrac

26、tion, because the helical structures determine the electrical properties of the MWCNT walls. It is found that the walls of some MWCNTs are all metallic, and the other MWCNTs contain metallic and semiconducting walls. But, on the other hand, high resolution TEM images show that many defects exist in

27、the two types of MWCNTs. The defects can affect the electrical properties of the MWCNTs and make them characteristic of semiconductors. Also, it is found that lattice images in high resolution TEM images of the sidewall zones of MWCNTs are not the structural ones but the results of the interference

28、between the diffraction waves of 0002 and . High resolution TEM images and their Fast Fourier Transform (FFT) images of the core zones of MWCNTs reflect the information of the helical angles of all of the walls in the MWCNTs, and are more advantageous to analyzing the chiralities.The unique interfac

29、ial structures of the Ni/MWCNT/a-CNT heterojunctions lead their electrical properties to be attractive. But, they consist of the three parts of metal nanowires, MWCNTs and a-CNTs, and their structures are complex. If they are connected into electrical circuits by metal electrodes, the structures wil

30、l become more complex. Therefore, the studies on their electrical properties started with the a-CNTs. It was found that the a-CNTs were amorphous semiconductors by using the dependence of their resistances on the temperature. Then, the electrical properties of the Ag/a-CNT heterojunctions were taken

31、 as a starting object for studying the electrical properties of the contacts between the a-CNTs and metals, where the Ag parts of the Ag/a-CNT heterojunctions in the AAO templates were defined as the lower part and the a-CNT parts were as the upper part. The surfaces of the AAO templates were partia

32、lly etched so that the roots of the Ag parts and the tips of the a-CNT parts were revealed. After this, metal films were evaporated on the Ag roots, and then the Ag roots were connected into the electrical system of a conductive atomic force microscope (AFM) by the metal films. The a-CNT tips were c

33、ontacted by the Pt coatings of the AFM tips, and so electrical circuits formed and the current-voltage characteristics of the heterojunctions were measured. It was found that there were two types of Ag/a-CNT heterojunctions, of which one had the linear current-voltage characteristic and the other had the symmetric and nonlinear. Further