【作者】 张春玲；

【导师】 李红东；

【作者基本信息】 吉林大学 ， 凝聚态物理， 2021， 硕士

【摘要】 自从石墨烯被成功制备以来,新型二维纳米膜材料一直是研究热点。二维纳米膜材料在物理、化学、光电、生物医学、传感器、超级电容器和电池等方面,具有重要的科学与应用价值。二维金刚石纳米膜是一种新的金刚石结构,其表面弛豫重构与电学性质密切相关,其已成为金刚石领域最活跃的研究方向之一。本文基于密度泛函理论,系统研究了硼终端二维(111)取向金刚石纳米膜结构稳定性与载流子迁移率等依赖于层数的变化规律。主要研究结果概括如下:1、基于第一性原理计算,我们考虑了两种硼终端二维金刚石(111)纳米膜结构,一种结构是一侧表面为硼终端,另一侧表面为氢终端(B-C-H)结构,第二种结构为两个表面都是硼终端(B-C-B)结构。计算B-C-H和B-C-B金刚石纳米膜的结构稳定性、电学性质及光学性质随着层数的变化规律。B-C-H结构(层数n≥2)和B-C-B结构(n≥3)具有动力学和热力学稳定性。硼终端金刚石纳米膜为直接带隙半导体,且能隙值为2.0—2.7 eV。相比于体金刚石材料其能隙减小,主要由表面硼能级导致的。价带顶主要由最外侧表面C原子和平面内扩展态的B原子贡献,导带底主要由最外侧B原子的局域态电荷贡献。2、基于形变势理论,计算二维B-C-H和B-C-B金刚石纳米膜结构的载流子迁移率。B-C-H和B-C-B纳米膜结构的电子迁移率分别为1.62-2.07×103 cm2·V.1·s-1和1.48-1.69×103 cm2·V-1·s-1,空穴迁移率分别为 4.05-6.40×102 cm2·V-1·s-1和3.33-6.59×102cm2·V-1·s-1。电子迁移率是空穴迁移率的3-4倍,有利于实现电子-空穴对的分离。从理论上证实硼终端能有效增加二维金刚石纳米膜的稳定性,调控电学性能、输运性质等,为进一步制备金刚石纳米器件提供了理论基础。更多还原

【Abstract】 Since the discovery of graphene,the two-dimensional nanomaterials have been the focus of research,which are widely used in physics,chemistry,optoelectronics,biomedicine,sensors,supercapacitors and batteries.In this paper,based on density functional theory,the thickness-dependent structure stability,electrical properties,optical properties,and carrier mobility of boron-terminated diamond(111)nano films are systematically studied.Two-dimensional diamond nano film is a novel structure,whose surface relaxation reconstruction determine electrical properties.It has become one of the most active research directions in the diamond field.The main research results are summarized as follows:1.Based on first-principles calculation,two kinds of boron-terminated diamond(111)nanofilms model are considered.In the first model,one surface is substituted by B atoms and another side is passivated by H atoms(named as B-C-H structure).In the second model,both C surfaces are substituted by B atoms(named as B-C-B structure).The structural,electronic properties and optical properties of B-C-H and B-C-B diamond nanofilms are investigated.It is reasonably stated that the B-C-H structures with n≥2 and B-C-B structures with n≥3 are dynamically and thermally stable.The nano films have direct bandgap characteristic,and their bandgaps are tunable in a region of 2.0-2.7 eV.The bandgaps are narrower than that of bulk diamond,being mainly related to the surface termination of boron atoms.The valence band maximum is mainly contributed by the outmost surface C atoms and B atoms with the extended state in the plane,while the conductance band minimum levels are mainly contributed by the localized charge from the outmost B atoms perpendicular to the surface.2.Based on the deformation potential theory,the carrier mobility values of the B-C-H and B-C-B diamond nanofilms are calculated.The electron mobility of B-C-H and B-C-B nanofilms structures are 1.62-2.07×103 cm2·V-1·s-1 and 1.48-1.69×03 cm2·V-1·s-1,respectively,and the hole mobility are 4.05-6.40×102 cm2·V-1·s-1 and 3.33-6.59×102 cm2·V-1·s-1,respectively.The electron mobility is 3-4 times higher than the hole mobility,the distinguished carrier mobilities between electron and hole are favorable for enhancing the effective separation of electron-hole pairs.It has been proved that boron-termination can effectively increase the stability of diamond nanofilms and effectively modulate the electrical properties and transport properties,which provides a broad application field for the further preparation of diamond-based nanometer devices.更多还原