【作者】 刘荣；

【导师】 田仁玉；

【作者基本信息】 华南理工大学 ， 材料物理与化学， 2013， 硕士

【摘要】 金刚石作为一种宽带隙、高硬度、高热导性的半导体材料，广泛应用于高能、高频、高温的环境下。近年来，与金刚石相关的研究不断推进，特别是在金刚石中引入缺陷形成的金刚石色心结构及其应用（例如金刚石NV色心）方面做了大量的理论和实验工作。而最近又有一种新的基于Cr基的单光子源发光器件表现出优于NV器件的性能，其微观结构在实验上目前尚未确定。本论文的主要工作是通过第一性原理计算结合晶体场理论和半导体理论等对金刚石色心单光子源发光器件的微观结构和相关电子结构进行探索和研究。本论文主要由以下四个章节构成：在第一章中概述了金刚石材料的研究背景和意义，详细介绍了国内外对于金刚石中的各类色心的研究进展，并着重阐述和比较了不同色心的微观结构及各类色心应用于单光子源的优缺点，并引出了本论文要做的主要工作。第二章中简单介绍了本论文工作所采用的理论计算方法和第一性原理软件（VASP）。在第三章中主要介绍了以下两个方面的工作：一、研究了单个Cr原子掺杂金刚石的结构稳定性以及电子结构。研究结果表明：在富碳的条件下，Cr₂V缺陷结构的形成能最低，而且研究发现Cr原子的d电子轨道和最近邻的C原子的p轨道之间有强烈杂化耦合作用，杂化后产生的杂质能级分布于金刚石的带隙中,而这有利于单光子源的发光中心的形成。二、研究了（Cr、N），（Cr、O），（Cr、N、O）共掺杂金刚石的结构稳定性以及电子结构。研究结果表明：在富氮的条件下，Cr₂V-NC缺陷结构的形成能最低，而且研究发现，Cr₂V-NC与Cr₂V缺陷的电子结构类似，所以N元素的引入可以提高金刚石单光子源的发光中心的产量。同时，研究结果还表明O原子的引入会在金刚石能带中产生一些能被热扰动激发的杂质带,影响发光性能。第四章研究了不同原子或者分子基团对金刚石（100）表面的修饰作用。通过计算发现，表面的化学性质对金刚石的电子结构影响很大。我们发现虽然在金刚石干净表面和其内部的NV缺陷之间没有明显电荷转移，但是由于表面和内部NV缺陷间的强烈的相互作用会使得其激发态的能级劈裂，这会使得1-价NV色心的零声子线变宽，不利于单光子的产生。而用H、OH、F、NH3及NH2修饰的后金刚石（100）表面在带隙中没有表面态，使得1-价NV色心的零声子线不受表面态的影响。并且吸附基团的电负性越大，表面对体性质的影响越小，预期使离表面较近的NV色心的发光性能越好。更多还原

【Abstract】 As a wide band-gap, high hardness and high thermal conductivity semiconductor,diamond is widely used in the environment of high energy, high frequency and hightemperature. Recently, there have been a lot of researches about diamond, especially thediamond color center defects, which involved many theoretical and experimental works. Morerecently, a new class of single photon emitters associated with chromium impurities indiamond showed a more remarkable performance than NV center. The atomic structure of theCr-related color center has not been confirmed. This dissertation is devoted to the atomicstructure and the electronic structure of diamond based single photon emitters fromfirst-principles, crystal field theory and semiconductor theory. The main contents are asfollowing with four chapters:We give a brief introduction to the research background and significance of diamondbased materials in chapter1. Mainly, the development of various kinds of color centers indiamond, and the atomic structure of each color centers and its merits and drawbacks in theapplication of single photon sources are discussed. Then we give an outline of thedissertation.In Chapter2, we present an introduction to the theoretical calculation method andfirst-principles code （VASP） used in our work.In chapter3, we mainly describe the following work:1. We investigate the structural stability and electronic structure of single chromium dopeddiamond. We find that the defect complex Cr₂Vis energetically favored under carbon-richcondition, and there is strong spin hybridization between carbon2p and Cr3d orbitals,which results in the defect levels located in the gap, and this favors the formation ofoptical centers.2. We investigate the structural stability and electronic structure of （Cr、N），（Cr、O），（Cr、N、O） co-doped diamond. We find that the defect complex Cr₂V-NCis energeticallyfavored under nitrogen-rich condition, and its electronic structure is found to be similar tothat of Cr₂V. The yield of optically active centers of single photon emitters could beimproved by incorporation of N. Meanwhile, the additional incorporation of oxygen to Cror （Cr,N） defects introduces not well-separated impurity levels, which will broaden theemission lines.In Chapter4, we investigate the surface decorations on diamond （100） surface with various atoms or molecules. We find that the chemical properties of surface have aremarkable influence on the diamond electronic structure. Though there is no obviouscharge transformation between the clean diamond surface and the inside NV defect, thestrong interaction between them will split the excited levels and then broaden the emissionlines, leading to a depletion of the single photon sources. As the H, OH, F, NH2, and NH3terminated （100） surfaces of diamond have no surface states in the band gap, the decoratedsurface will not interfere the zero-photon-line of NV-defect. It is found that the largerelectronic affinity of adsorbates, the better effect of decoration.更多还原