【作者】 程立；

【导师】 常海欣；

【作者基本信息】 华中科技大学 ， 材料工程， 2020， 硕士

【摘要】 自从著名物理学家、诺贝尔奖获得者理查德·费因曼在1959年提出“纳米科学与技术”以来,人们对于物质世界的研究逐渐由宏观走向微观,而随着应用科学的不断发展,人类对微观世界的观察手段日益丰富,在尺寸方面也逐渐逼近理论极限,人们由最开始的从分子、原子层面对世界的认识,逐步发展为在纳米尺度上对材料性能的最本征的解释,再到试图通过对材料在纳米尺度层面进行调控以期获得需要的材料性能,纳米科技已经在众多方面产生了广泛而深远的影响。近年来,二维材料由于具有独特的光电及化学性质而引起人们越来越多的研究兴趣,二维材料在结构上可以分为层状结构和非层状结构,即范德华结构与非范德华结构,由于层与层之间的范德华力相对薄弱,便于二维材料的可控制备,使得二维层状材料被越来越多的人研究。二维材料的的制备方法可以概括为自上而下、自下而上两种,前者主要包括物理剥离法、液相剥离法和插层剥离法法,对于二维层状材料,制备方法相对简单,但是近年来,由于非层状二维材料具备奇特的物理性能、较高的柔性以及与硅基电子技术的良好兼容性,使其成为研究的热点之一,然而,从非层状晶体中实现二维结构仍然是一个挑战,这就要求打破大块晶体的对称性,保证晶体高度的各向异性生长。本文以Ⅱ-Ⅵ族过渡金属硫化物为研究对象,选取作为非范德华结构的CdTe、ZnTe为研究材料,以达到省时、稳定、高效、可控的CVD外延生长出高质量的单晶为目标,成功制备出产率高、质量好的CdTe单晶,并在此基础上对工艺方法进行创新,首次采用限域的CVD外延生长方法成功合成出高质量的ZnTe单晶,研究表明,采用CVD外延的生长方法可以实现非范德华结构材料的超薄制备,在稳定获得高产率单晶的同时,还可以将工艺周期由传统烧结法所需的一周缩短至3h,此外,对CVD外延生长的衬底材料SiO2/Si和云母进行了对比,实验表明,在云母衬底上生长的单晶的产率更高、质量更好,这是因为云母的表面（001）没有悬空键,从而实现了被吸附原子沿云母表面的小迁移能垒,促进了被吸附原子的高速迁移和非层状材料的快速横向生长。在CVD外延生长CdTe单晶的基础上,进一步研究了掺杂过渡金属元素（M）对CdTe性质的影响,通过大量实验对CdTe稀磁半导体的制备工艺进行了探索,结果表明,在一定温度条件下可以实现不同M元素掺杂比例的Cd_1-xM_xTe单晶的制备,XRD图显示晶格常数随着掺杂浓度增加而减小,这是由于M原子半径小于Cd原子半径引起的晶格萎缩所致。在300K温度下,采用VSM对Cd_1-xM_xTe单晶的磁学性质进行测试,结果表明,磁矩随着不同掺杂比例的M呈减小趋势,这是由于M离子占据间隙位,从而导致磁矩的减小和铁磁行为的减弱。更多还原

【Abstract】 Ever since the famous physicist and Nobel Prize winner Richard Feynman proposed "Nano Science andTechnology" in 1959,people’s research on the material world has gradually changed from macro to micro,and with the continuous development of applied science Human beings are increasingly observing the micro world,and they are gradually approaching the theoretical limit in terms of size.From the initial understanding of the world at the molecular and atomic levels,people have gradually developed into the most intrinsic interpretation of the performance of materials on the nanoscale,And then try to adjust the materials at the nano-scale level in order to obtain the required material properties,nanotechnology has produced a wide and far-reaching impact in many ways.In recent years,two-dimensional materials have attracted more and more research interest due to their unique photoelectric and chemical properties.Two-dimensional materials can be divided into layered structures and non-layered structures in structure,that is,van der Waals structures and non-van der Waals structures.Because the van der Waals force between layers is relatively weak,which facilitates the controllable preparation of two-dimensional materials,two-dimensional layered materials are being studied by more and more people.The preparation method of two-dimensional materials can be summarized as top-down and bottom-up.The former mainly includes physical peeling method,liquid-phase peeling method and interlayer peeling method.For two-dimensional layered materials,the preparation method is relatively Simple,but in recent years,due to its peculiar physical properties,high flexibility and good compatibility with silicon-based electronic technology,non-layered two-dimensional materials have made it one of the research hotspots.The realization of the twodimensional structure is still a challenge,which requires breaking the symmetry of the bulk crystal and ensuring the highly anisotropic growth of the crystal.In this paper,the Ⅱ-Ⅵ transition metal sulfide is taken as the research object,and CdTe and ZnTe as non-van der Waals structures are selected as the research materials,in order to achieve time-saving,stable,efficient and controllable CVD epitaxial growth of high-quality single crystals as the goal,CdTe single crystal with high yield and good quality was successfully prepared,and on this basis,the process method was innovated.For the first time,the CVD epitaxial growth method with limited domain was used to successfully synthesize high-quality ZnTe single crystal.The growth method can realize the ultra-thin preparation of non-van der Waals structure materials,while stably obtaining high-yield single crystals,and the process cycle can be shortened from the week required by the traditional sintering method to 3h.In addition,for CVD epitaxially grown substrates The materials SiO2/Si and mica are compared.The experiment shows that the single crystal grown on the mica substrate has a higher yield and better quality.This is because the surface(001)of the mica has no dangling bonds,thereby achieving adsorption The small migration energy barrier of atoms along the surface of mica promotes the high-speed migration of adsorbed atoms and the rapid lateral growth of non-layered materials.Based on the epitaxial growth of CdTe single crystal by CVD,the effect of doping transition metal element(M)on the properties of CdTe was further studied.The preparation process of CdTe dilute magnetic semiconductor was explored through a large number of experiments.As a result,the surface was under certain temperature conditions.The preparation of Cd1-xMxTe single crystals with different doping ratios of M elements can be achieved under certain temperature.XRD shows that the lattice constant decreases with increasing doping concentration,which is due to the lattice shrinkage caused by the radius of M atoms being smaller than the radius of Cd atoms.At 300K,the magnetic properties of Cd1-xMxTe single crystals were tested using VSM.The results show that the magnetic moment decreases with different doping ratios of M.This is because M ions occupy gaps,resulting in magnetic Moment reduction and weakening of ferromagnetic behavior.更多还原