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ZnTe一维纳米结构的制备、表征及电学特性
Alternative TitleSynthesis, characterization and electrical properties of ZnTe one-dimensional nanostructures
孟清芳
Subtype博士
Thesis Advisor毛星原
2008-12-26
Degree Grantor中国科学院金属研究所
Place of Conferral金属研究所
Degree Discipline材料物理与化学
KeywordZnte纳米线 一维纳米结构 欧姆接触 掺杂 导电原子力显微镜
Abstract本文以ZnTe一维纳米材料为研究体系,对ZnTe一维纳米材料的制备,微观结构表征,生长机理,光学性能等基本特性进行研究。利用氢助热蒸发的方法制备了周期孪晶纳米线和均匀纳米带的闪锌矿ZnTe一维纳米结构。采用X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、透射电镜(TEM)、高分辨透射电镜(HRTEM)和能谱(EDS)等多种手段对产物进行表征和分析,发现孪晶纳米线主要沿<111>方向生长;而均匀纳米带沿<111>和<211>方向生长。在此基础上建立了不同形态产物的生长模型,并从温度、接触角、相图、能量等角度探讨产物的形成机理。发现不同形态纳米结构的形成主要依赖于其基体的生长温度。周期孪晶纳米线和均匀纳米带分别位于低温和高温区域,而且在其交界区发现了由孪晶纳米线向均匀纳米带过渡的纳米结构。拉曼光谱的结果进一步证实了孪晶界是由过量的Te原子构成。孪晶和过量的Te原子导致了光致发光光谱向长波方向发生了微弱的“红移”,这使得ZnTe一维纳米结构在纳米器件上具有潜在的应用价值。 ZnTe纳米线的电学特性研究主要针对纳米线与金属电极的欧姆接触、纳米线本征电阻率、光电导、掺杂提高纳米线导电率等多个问题展开。尝试利用Au、Pt、Ni等多种电极解决ZnTe纳米线的欧姆接触问题,最终发现Ni/Au电极可以实现ZnTe纳米线与电极间的欧姆接触。采用四电极法测量了单根ZnTe纳米线的伏安特性曲线,计算出ZnTe纳米线与Ni/Au电极的接触电阻率为2.6×10-1 Ωcm2,而其本征电阻率为369.1 Ωcm。利用可调光源测量单根ZnTe纳米线的光电导特性曲线,发现ZnTe纳米线具有典型的光电特性,在强度为36.4 mW/cm2的白光照射下,低阻和高阻纳米线的电导分别提高了36.7%和2个数量级。在此基础上,进一步研究了ZnTe纳米线的开关特性,但其频率响应较低。 采用Se和Cu两种元素对ZnTe纳米线进行掺杂,发现掺杂后ZnTe纳米线的电导率均可以得到有效的提高。利用ZnTe纳米线与ZnSe纳米线生长过程中存在的交叠区间,将Se掺杂进入ZnTe纳米线。结果发现,掺杂量为3.22%时,ZnTe纳米线电导率相对未掺杂时提高了2个数量级。而掺杂Cu时,采用热扩散的方法使Cu均匀扩散进入ZnTe纳米线,发现当Cu的掺杂量为17.5%时,其电导率提高了5个数量级。 最后利用导电原子力显微镜法,通过自制Au导电针尖初步测量了Cu掺杂ZnTe纳米线的电阻率。导电原子力显微镜法的测量结果为5.8 × 10-3 Ωcm,与四电极法的测量结果3.4 × 10-3 Ωcm处在相同数量级。 以上的工作结果,为ZnTe纳米线在纳电子器件的应用提供了丰富的实验和理论基础。
Other AbstractIn this dissertation, the synthesis, characterization, growth mechanism and optical properties of ZnTe one-dimensional nanostructures have been investigated. Zinc-blende-structured ZnTe one-dimensional nanostructures, periodically twinned nanowires and uniform nanoribbons, have been synthesized. The products have been characterized by XRD, FE-SEM, TEM, HRTEM, and EDS. It has been found that periodically twinned ZnTe nanowires grow mainly along <111> direction, while the uniform nanobelts grow along <111> and <211> directions. Based on the results, the growth model of the as-grown products with various morphologies was founded, and the growth mechanism was discussed from the point views of local temperature, contact angle, phase equilibrium diagram and energy, etc. The formation of various nanostructures was proved to be dependent on the local temperature. Periodically twinned nanowires and uniform nanoribbons dominate at low- and high-temperature zone, respectively. Moreover, the transition from the twinned nanowire to the uniform nanoribbon takes place at the middle temperature zone. Optical properties of ZnTe nanostructures have been investigated by Raman spectrum and photoluminescence (PL) spectrum. Raman spectrum confirms that the existence of Te peaks result from the existence of twin boundaries in the specimen. The emission of ZnTe nanostructures in PL spectrum has a slight red shift from the bandgap emission of bulk materials, which provides a potential application in nanodevices. The electrical properties of ZnTe nanowires mainly involve the ohmic contact between nanowires and metal electrodes, the specific intrinsic resistivity, photoconductivity, doping to improve the conductivity, etc. Although Au, Pt, and Ni have been tried as electrodes, Ohmic contacts to individual ZnTe nanowire are formed using Ni/Au multi-layer electrodes finally. Four-terminal measurements have been used to investigate the current-voltage characteristics of contacts and nanowires. Specific contact resistivity of Ni/Au contacts is ~2.6×10-1 Ωcm2 and the intrinsic resistivity of the individual ZnTe nanowire is ~369.1 Ωcm. The photoconductivity characteristic curves of individual ZnTe nanowires have been measured under white light with different intensities, and the typical photoconductivity behavior is observed. The photoconductivity of individual ZnTe nanowires with low- and high-resistance has a 36.7% and 2 orders of magnitude improvement with a light intensity of 36.4 mW/cm2, respectively. The optical switch properties of individual ZnTe nanowires are also discovered, but the frequency response is much low. Se and Cu doping have been used to improve the conductivity of ZnTe nanowire, and the results indicate that both Se and Cu doped ZnTe nanowires are effectively improved. Se doping is the growth process of ZnSe and ZnTe nanowires in the same tube furnace, and Se will be doped into ZnTe nanowires during the growth process, because there is an overlapping growth region between ZnSe and ZnTe. However, another way is adopted in Cu doping. Cu will be diffused into ZnTe nanowires easily during the heat treatment process. Cu content is controlled by the thickness of Cu layer sputtering on the top of ZnTe nanowires. I-V curves of Se and Cu doped ZnTe nanowires have been also tested by four-terminal measurement. The results indicate that when Se and Cu doping content in ZnTe nanowires is 3.22% and 17.5%, there is a two and five orders of magnitude improvement in the conductivity of Se and Cu doped ZnTe nanowires, respectively. Finally, the resistivity of individual Cu doped nanowires has been investigated by conductive atomic force microscope (CAFM) with self-made Au conducting tip. The resistivity obtained with CAFM and four-terminal measurement is 5.8 × 10-3 Ωcm and 3.4 × 10-3 Ωcm, respectively, which are in the same order of magnitude. All the work mentioned above provides much practical and theoretical basis for the application of ZnTe nanowires in nanodevices.
Pages94
Language中文
Document Type学位论文
Identifierhttp://ir.imr.ac.cn/handle/321006/17035
Collection中国科学院金属研究所
Recommended Citation
GB/T 7714
孟清芳. ZnTe一维纳米结构的制备、表征及电学特性[D]. 金属研究所. 中国科学院金属研究所,2008.
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