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类型 基础研究 预答辩日期 2017-11-23
开始(开题)日期 2016-04-01 论文结束日期 2017-09-21
地点 田家炳南楼205 论文选题来源 973、863项目     论文字数 2 (万字)
题目 二维过渡金属硫属化合物的合成及光学表征
主题词 过渡金属硫属化合物,化学气相沉积,光致发光,缺陷,迁移率
摘要 过渡金属族硫属元素化合物(TMD)以其丰富多样的光学和电学运输等物理特性为光电应用提供了无限可能。原子级别厚度的TMD具有覆盖可见到近红外范围的卓越光吸收和发射能力,有望应用于光电器件领域,譬如光电检测器,光伏发光器和光发射器等等。化学气相沉积(CVD)是行之有效的大规模生产高品质单晶TMD薄膜的方法。在本论文中,我们研究了MoS2,WS2和ReS2的CVD生长及生长样品的光学和电学性质,并进行了样品质量和生长条件与光学和电学性的相关性研究。 首先,提出了一种用于评估CVD生长MoS2的本征光学质量的光谱学方法。通过低温缺陷诱导的束缚态激子发射表征,建立了晶体尺寸和生长温度与CVD生长MoS2单晶中的结构缺陷数量的关系,研究表明结构缺陷数量与CVD生长MoS2在空气和真空中的PL强度的差异相关。除此之外,我们的研究结果表明 CVD 生长MoS2的结构缺陷不仅影响其光学质量,还会影响其电学性能。这种方法亦适用于评估MoS2之外的TMD材料的固有光学质量。 其次,本文通过改变引入CVD系统的硫(S)蒸气的总量和前置反应时间来生长出可控的单层,双层以及多层单晶WS2,从而实现最佳参数的调控以用于生产具有可控形状和尺寸以及厚度的WS2晶粒。利用可调控生长机制生长出的不同形状,尺寸以及厚度的单晶WS2表明了我们的生长方法的先进性和可操作性。此外,基于层数变化的WS2场效应管迁移率调控和具有优异光响应的三层WS2纳米片的高性能光电晶体管也进一步展示了本文的生长方法在TMD光电器件上的实际应用。 最后,本论文报道了具有相同晶格对称性(即WS2 / MoS2)和不同晶格对称性(ReS2 / MoS2)的原子层面内异质结构的可扩展两步气相生长方法。本文使用拉曼散射和光致发光光谱来验证横向异质结生长质量。研究表明该原生异质结构是p-n结,并具有新颖的器件的潜力。 本论文目前报道的基于TMD的工作不仅为进一步合成其他TMD和异质结构的过程提供了研究基础,同时也为对二维半导体的光学和电学性质研究及其在电子和光电领域的潜在应用提供了前置性实验。
英文题目 Synthesis and optical characterization of two dimensional transition metal dichalcogenides
英文主题词 Transition metal dichalcogenides, Chemical vapor deposition, Photoluminescence, Defect, mobility
英文摘要 The rich and diverse physics of transition metal dichalcogenides (TMDs) together with their novel optical and electrical transport properties offers unprecedented opportunities for electronic and optoelectronic applications . Atomically thin TMDs are characterized by attractive band gaps exhibiting extraordinary light absorption and emission properties covering the visible to near-infrared range, making them promising candidates for optoelectronic devices such as photodetectors, photovoltaics, and light emitters. Chemical vapor deposition (CVD) is the most promising method to produce TMD large-scale films or high-quality single crystals. In this study, we investigated the fundamental optical and electrical properties of CVD grown MoS2, WS2 and ReS2,which are strongly correlated to the sample quality and growth conditions. Firstly, a systematic spectroscopic approach for the evaluation of intrinsic optical quality of CVD grown MoS2is presented. The amount of structural defects in CVD grown MoS2single crystals with different crystal sizes and growth temperatures was established by low-temperature defect-induced bound-excitonemission, which correlated well with the difference in PL intensities measured in air and vacuum. The structural defects in CVD MoS2 could affect not only its optical quality but also its electrical performance, as demonstrated by electrical transport measurements. This approach is applicable to assess the intrinsic optical quality of MoS2and other TMDs materials. Secondly, we produced single-, bi- and few-layered WS2 single crystals by varying the time of introducing sulfur (S) vapor into the CVD system, S-precursor amount and S-precursor exposure time, in order to determine the most optimum combination of these parameters for producing as-grown WS2 grains with the most appropriate shape and size. Single-step growth providing better controllability of the chalcogen precursor allows the fine tuning of layer number and crystal quality. The production of different shapes of single-crystal WS2 with a viable growth mechanism, and a thickness and size that can be easily varied, suggests the versatility of our growth strategy. Furthermore, the calculated field effect mobilities based on layer number and the demonstration of a high performance phototransistor based on trilayer WS2nanosheet with prominent photoresponse facilitate the practical application of our growth recipe to other TMDs. Lastly, a scalable, two-step vapor phase growth process of in-plane heterostructures of atomic layers with the same lattice symmetry (i.e. WS2/MoS2) and different lattice symmetry (ReS2/MoS2) is reported. Raman and photoluminescence spectroscopies have been employed to verify the lateral heterojunctions. The as-grown heterostructures are further demonstrated to be p-n junctions, indicating their potential for novel devices. The present work on these TMD layers not only provides a foundation to further develop processes for the synthesis of other TMDs and heterostructure salong with a critical understanding on the optical and electrical properties of 2D semiconductors but also opens up many opportunities for their potential applications in atomically thin electronic and optoelectronic devices.
学术讨论
主办单位时间地点报告人报告主题
物理系 2016-03-18 田家炳南楼203 Amina Zafar Chemical Vapour Deposition of Tungsten Disulphide (WS2)
物理系 2016-04-09 田家炳南楼203 Amina Zafar Synthesis of MoxW1-xS2 Alloy Nanosheets by Chemical Vapour Deposition
物理系 2017-01-02 田家炳南楼203 Amina Zafar TMDs Heterostructures
物理系 2016-07-04 田家炳南楼203 刘杰 Selective Growth of Semiconducting Single-walled Carbon Nanotubes
物理系 2016-05-25 田家炳南楼203 Boris I. Yakobson Predictive modeling in 2D materials: morphology, dislocations, grain boundaries
物理系 2016-05-24 田家炳南楼203 Hua Zhang Synthesis and Applications of Novel Two-Dimensional Nanomaterials
物理系 2015-12-09 田家炳南楼203 Dr. Alister J. Page Catalysts, Etchants and Magnetic Fields: How can Carbon Nanostructure Growth be Controlled?
物理系 2017-03-26 田家炳南楼203 Amina Zafar Photocurrent of CVD-WS2
     
学术会议
会议名称时间地点本人报告本人报告题目
ICPS 2016-08-04 Beijing International Convention Center, Beijing, China Synthesis and optical properties of CVD MoS2
Edison 20 2017-07-17 Buffalo, NY, USA Probing the intrinsic optical quality of CVD grown MoS2
     
代表作
论文名称
Probing the intrinsic optical quality of CVD MOS2
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
缪峰 正高 教授 博导 南京大学
董晓臣 正高 教授 博导 南京工业大学
马延文 正高 教授 博导 南京邮电大学
王肖沐 正高 教授 博导 南京大学
李孝峰 正高 教授 博导 苏州大学
游雨蒙 正高 教授 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
吕俊鹏 正高 教授 东南大学