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面向二硫化钼器件的微纳操控与制造技术研究
Alternative TitleResearch on Micro/nano Manipulation and Manufacturing Technology for Molybdenum Disulfide Devices
李萌
Department机器人学研究室
Keyword原子力显微镜 二硫化钼 晶向检测 深度可控加工 器件装配
Pages174页
Degree Discipline模式识别与智能系统
Degree Name博士
2018-11-28
Degree Grantor中国科学院沈阳自动化研究所
Place of Conferral沈阳
Abstract在众多纳米材料中,以石墨烯、过渡金属硫化物等为代表的二维材料,由于具有一系列优异的特性,特别是卓越的电学性能,引起了研究者们极大的兴趣。随着研究深入,人们发现石墨烯零带隙特性,给电学方面的应用带来极大困难。相比之下,其他二维材料,比如过渡金属硫化物,则天然具有带隙。此外该类材料在化学,材料,物理等诸领域甚至具备比石墨烯更为优异的表现,有希望替代石墨烯,成为未来新一代半导体材料。作为过渡金属硫化物中最具代表性的材料—二硫化钼,具备这一族材料的典型特征,比如随层数可调带隙,优异的光电特性,能够通过机械剥离手段获得单层及多层结构。另外,二硫化钼的原材料储量丰富,成本低廉,能够满足该种材料大规模使用的要求,同时制得的样本稳定性良好,能够长时间保存的。基于上述原因,本文以二硫化钼作为研究目标,基于未来器件制造定制化、功能多元化要求,制定了二硫化钼纳米片的合理加工路线,在全面分析当前技术存在的各方面不足之后,结合加工平台提出了切实可行的改进措施,分别从晶向检测技术、可控深度加工技术以及器件装配技术等三个方面开展了如下的研究工作:(1)二硫化钼晶向与摩擦力的映射关系及与二硫化钼层数相关的电学性能的研究。获得二硫化钼的晶向相关量,并建立起与晶向之间的映射关系,是对二硫化钼进行快速晶向检测的前提条件。同样,理论上对二硫化钼的层数对其电学性能进行分析,给出最优层数的范围,能够为后续二硫化钼的加工制作提供理论依据。本文基于纳米机器人操作平台,研究了原子力显微镜(Atomic Force Microscope,AFM)探针与二硫化钼表面运动模型,结合二硫化钼表面原子构成,建立了完整的针尖-晶向之间的映射关系,并通过仿真得到二硫化钼各个晶向的摩擦力信号,获得与晶向相关的摩擦力特征;根据二硫化钼的多层结构与电极之间构成的电阻网络模型,对随层数变化的器件迁移率机理进行分析,获得二硫化钼不同条件下的迁移率变化曲线。(2)基于频域特征的二硫化钼快速晶向检测技术。现有晶向检测技术通常依赖于样本表面的清晰成像,对样本制备有较高要求,成像条件苛刻、检测过程复杂,不具备快速、灵活及普适性的要求。本文基于二硫化钼晶向与摩擦力之间的理论映射关系,通过二硫化钼表面原子力成像,获得与晶向相关的真实摩擦力信号,并通过快速傅里叶变换处理,进一步获得与晶向对应的信号频域特征,引入误差分析公式,结合一系列判定方法,最终建立完整的晶向检测技术,并通过实验验证了该方法的有效性及实用性。(3)利用AFM对二硫化钼可控深度的加工。为了实现二硫化钼的可控深度加工,同时与晶向检测技术更好地结合,本文利用AFM系统分别采用了直接加工模式及超声振动相位反馈模式对单层、多层二硫化钼进行不同深度的加工。本文建立了两种加工方式下的加工预估过程,即在加工之前,根据加工机理及实际加工结果建立起加工深度与切割力或者相位之间的对应关系,并由此确定加工参数,提高加工深度的精确度。同时全面分析对比了两种加工方式加工过程以及加工结果,并总结了两种方式的优点及不足之处。最后,与晶向检测技术相结合,实现沿特定晶向进行目标深度的精确加工。(4)二硫化钼纳米片的器件装配技术研究。以电子束刻蚀技术为代表的传统器件装配技术,存在很多无法避免的问题,比如装配过程复杂,需要多次使用掩膜版,并且在使用过程中,电子束会在材料表面产生污染与缺陷等等。本文首先采用AFM直接加工与剥离工艺相结合的方法,实现二硫化钼与电极之间的装配,构成器件。由于装配成功率低,本文又同时利用光诱导介电泳平台,实现了不同厚度的二硫化钼纳米片与不同金属电极的快速器件装配,分析了电极粗糙度以及二硫化钼纳米片的厚度对器件性能的影响,验证了随层数变化器件迁移率的相关理论。本文将理论建模与实验研究结果相结合,围绕着定制化器件加工的两个核心问题,即不同晶向及不同深度地精确控制,提出了切实可行的晶向检测技术、可控深度的加工技术,同时结合器件装配技术,为未来利用二硫化钼进行纳米器件精确可控的大规模加工制造提供了技术支持。
Other AbstractAmong the large number of nanomaterials, two dimensional materials, such as graphene and transition metal sulfide, have attracted great interest due to a series of excellent properties, especially excellent electrical properties. After years of deep research, the zero band gap characteristic of grapheme has been discovered, which bring great difficulties to the electronic application. In contrast, other two-dimensional materials, such as transition metal sulfides, naturally own band gaps. More importantly, these materials have even better performance than graphene in chemical, material, physical and many other fields. Therefore, these materials are the most promising candidate to replace graphene and become the new generation of semiconductor materials in the future. As the most representative material in transition metal sulfides, molybdenum disulfide (MoS2) owns the typical characteristics of this group of materials, such as the adjustable band gap with the number of layers, excellent photoelectric properties, and the ability to obtain monolayer and multi-layer structures by mechanical peeling. Moreover, the raw material of MoS2 is abundant and relatively low-cost, which can meet the requirement of large scale use. Additionally, MoS2 have good stability and the obtained samples can be preserved under ambient condition for a long time. Based on the above reasons, MoS2 has been chosen as the research target. In respect to the customization and functional diversification requirement for the future device manufacturing, the rational processing route for MoS2 nanosheets is formulated. After thoroughly analyzing the shortcomings of the current technology, the practical improvement measures are deployed based on our processing platform, The following research work has been carried out in three aspects: lattice orientation detection technology, controllable depth processing technology and device assembly technology. (1)Research on the mapping relationship between MoS2 lattice orientation and friction and electrical properties related to number of layers: Obtaining the lattice orientation correlation and establishing the mapping relationship of the lattice orientation are the necessary prerequisite for developing a fast lattice orientation detection technology of MoS2. In the same way, the electrical performance of MoS2 should be theoretically analyzed and the range of the optimal layer should be given, which can provide the theoretical basis for the subsequent processing of MoS2. Therefore, the motion model between the AFM probe and the MoS2 surface was studied based on AFM platform. Considering the surface atom distribution of MoS2, the mapping relationship between the tip and the lattice orientation was firstly established. Through the simulation, the friction signal along each orientation and the corresponding friction characteristics were obtained. According to the structure of multilayer MoS2 and the resistance network model between the electrode and MoS2 nanosheet, the structure of the crystal direction is obtained. Based on the resistance network model, the underlying mechanism that device mobility varying with the number of layers was analyzed, and the mobility curves of MoS2 under different conditions were obtained. (2) Fast lattice orientation detection technology of MoS2 based on frequency domain characteristics: The existing lattice orientation detection technology usually depends on the clear imaging of the sample surface. Furthermore, the requirement for the sample preparation and imaging conditions are extremely high, and the detection process is relatively complex. In short, current lattice orientation detection technology obviously fails to satisfy the rapid, flexible and universal requirement. In this dissertation, based on the theoretical mapping relation between MoS2 lattice orientation and friction force, the real friction signal related to lattice orientation was obtained through the MoS2 surface atomic force imaging. Moreover, the frequency characteristics corresponding to the lattice orientation were obtained by fast Fourier transform. By introducing the error analysis formula and combing with a series of determination methods, a complete orientation detection technique was eventually established. The effectiveness and practicability of the method were verified by experiments. (3) Controllable depth fabrication of MoS2 by AFM: In order to realize the controllable depth fabrication of MoS2 and well combine with the lattice orientation detection technology, this dissertation has adopted the direct machining mode and the ultrasonic vibration phase feedback mode to process the monolayer and multilayer MoS2 nanosheets with various depth by using the AFM system. Pre-estimation process with two processing modes was established, that is, before processing, the corresponding relationship between the machining depth and the cutting force or phase is established according to the machining mechanism and the actual processing results, and the fabrication parameters were determined. In this way, the precision of the machining depth was improved. At the same time, the machining process and results of the two modes were comprehensively compared, and the advantages and disadvantages were summarized. Finally, combining with the lattice orientation detection technology, precise fabrication with target depth along specific crystal direction was realized. (4) Research on device assembling technology of MoS2 nanosheets: Conventional device assembling technology that represented by EBL(electron beam lithography), has many unavoidable problems, such as the complexity of the assembly process, multiple use of the masks, easily producing pollution and defects on material surface during the fabrication. Firstly, the assembling between MoS2 nanosheets and electrode was realized by combining the direct fabrication mode of AFM and lift-off process. Because of the low assembling rate and poor performance, this dissertation has adopted ODEP platform to realize fast device assembling of MoS2 nanosheets with various thickness and different metal electrodes. The influence of the roughness of electrode and the thickness of MoS2 nanosheets on the device performance was analyzed, and the mechanism underlying the variation of the device mobility with the number of layers was verified. In this dissertation, theoretical modeling and experimental results were combined, aiming at resolving the two core problems to realize the device customization, namely, precise control on various lattice orientation and depth. The feasible lattice orientation detection technology and the controllable depth fabrication technology were put forward. These technologies, together with the device assembling, have provided the technical support for the precise controllable large-scale machining of MoS2 nanosheets in the future.
Language中文
Contribution Rank1
Document Type学位论文
Identifierhttp://ir.sia.cn/handle/173321/23648
Collection机器人学研究室
Recommended Citation
GB/T 7714
李萌. 面向二硫化钼器件的微纳操控与制造技术研究[D]. 沈阳. 中国科学院沈阳自动化研究所,2018.
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