快重离子辐照对MoS2热导率的影响研究

利用0.97 GeV的209Bi离子辐照二硫化钼（MoS₂）晶体,辐照注量范围为1×1010～1×1012 ions/cm2,结合原子力显微镜（AFM）观测和Raman光谱分析研究了快重离子辐照对MoS₂热导率的影响。实验结果显示,快重离子辐照在MoS₂中产生了潜径迹,较高激光功率下的Raman测试使样品局部温度升高,导致E_1/2g和A_1g峰随注量增加向低波数方向移动,且峰形展宽。引入了通过改变激光功率测量Raman光谱得到MoS₂热导率的计算方法,获得了不同辐照注量下MoS₂的热导率的定量分析结果,随注量增加,热导率不断降低,从未辐照样品的563 W/mK下降到1×1012 ions/cm2辐照时的132 W/mK。Molybdenum disulphide (MoS₂) was irradiated by 0.97 GeV 209Bi ions with the fluence of 1×1010 to 1×1012 ions/cm2. The irradiation effect on the thermal conductivity of MoS₂ was analyzed by atomic force microscope (AFM) and Raman spectroscopy. The experimental results show that hillock-like latent tracks are observed on irradiated MoS₂ by AFM. The measurement of MoS₂ by Raman spectrometer with high laser power results in the increase of local temperature of MoS₂, which cause the downshift of peaks position and broadening of E_1/2g and A_1g peak. Furthermore, according to Raman spectra measured at different laser power, thermal conductivity of MoS₂ before and after irradiation was calculated, which show that the thermal conductivity of MoS₂ decreases with increasing fluence, from 563 to 132 W/mK for pristine and 1×1012 ions/cm2 irradiated MoS₂, respectively.     

MoS2/SiO2界面黏附性能的尺寸和温度效应

探索二维材料与其衬底之间的黏附性能对于二维材料的制备、转移以及器件性能的优化至关重要.本文基于原子键弛豫理论和连续介质力学方法,系统研究了尺寸和温度对MoS₂/SiO₂界面黏附性能的影响.结果表明,由于表面效应引起的热膨胀系数、晶格应变和杨氏模量的变化, MoS₂/SiO₂界面黏附能随MoS₂厚度的减小而增大,而热应变使MoS₂/SiO₂界面黏附能随温度的升高而逐渐降低.此外,预测了在不同尺寸和温度下MoS₂在SiO₂衬底上的“脱落”条件,系统阐述了MoS₂与SiO₂衬底之间黏附性能的物理机制,为基于二维材料电子器件的优化设计提供了理论基础.     

脉冲磁控溅射MoS2-Ti涂层常温及高温真空摩擦磨损性能

利用脉冲磁控溅射法，以铝青铜合金(C63200)和硅片为基底，制作不同Ti含量的MoS₂-Ti复合涂层。通过XRD、SEM、EDS、光学显微镜、多环境摩擦试验机等表征了涂层的结构成分和摩擦性能。结果表明：随Ti含量的增加，涂层致密度提升，S、Mo原子比上升。Ti的掺入使涂层由高度结晶态向非晶态转变。Ti含量增加，涂层摩擦磨损性能先上升再下降，常温真空下含3%Ti的涂层拥有稳定和低至0.015的摩擦系数，23%Ti的涂层失去润滑性。温度升高到400℃，涂层摩擦系数由0.015~0.04上升至0.07~0.1，含13%Ti的涂层高温真空下在800s后润滑失效。磨痕形貌显示，含3%Ti的涂层磨痕最窄，温度升高宽度增加不大，含13%Ti的涂层磨损严重，400℃真空环境下很快磨穿，纯MoS₂和13%Ti涂层摩擦时发现大量磨粒和破碎磨屑。     

Cr和W掺杂的单层MoS2电子结构的第一性原理研究

采用密度泛函理论框架下的第一性原理平面波赝势方法, 研究了Cr和W掺杂对单层二硫化钼(MoS₂)晶体的电子结构性质的影响. 计算结果表明: 当掺杂浓度较高时, W对MoS₂的能带结构几乎没有影响, 而Cr的掺杂则影响很大, 表现为能带由直接带隙变为间接带隙, 且禁带宽度减小. 通过进一步分析, 得出应力的产生是导致Cr掺杂的MoS₂电子结构变化的最直接的原因.     

二硫化钼量子点的一步水热法制备与光学性能研究

二硫化钼量子点(MoS₂ QDs)因具有尺寸可控、量子限域效应强等优异的物化特性，故在传感、荧光检测和光催化等领域中具有潜在的应用价值。以钼酸铵为钼源，以谷胱甘肽为硫源，采用一步水热法合成水溶性好、尺寸均一的MoS₂QDs(MoS₂ QDs-1)。为探究不同硫源对MoS₂ QDs尺寸和光学性能的影响，又以钼酸铵和L-半胱氨酸分别为钼源和硫源，通过相同方法制备MoS₂ QDs(MoS₂ QDs-2)。研究了MoS₂ QDs-1和MoS₂ QDs-2样品的结构和光致发光性能。结果表明，与MoS₂ QDs-2样品相比，MoS₂ QDs-1样品的平均晶粒尺寸更小(3.88 nm)、平均晶粒高度更低(4.75 nm)、光学带隙更小(3.65 eV)和荧光量子产率更高(10.8%)。     

低温下二硫化钼电子迁移率研究

二硫化钼(MoS₂)是已知的二维半导体材料中光电性能最优秀的材料之一. 单原子层厚的MoS₂是禁带宽度为1.8 eV 的二维直接带隙半导体材料, 可以用来发展新型的纳米电子器件和光电功能器件. 本论文利用玻尔兹曼平衡方程输运理论研究低温时MoS₂系统的电输运性质, 计算得到了MoS₂电子迁移率的解析表达式. 研究发现, 低温时MoS₂ 的迁移率与衬底材料的介电常数的平方成正比; 与系统的电子浓度对带电杂质的浓度的比率n_e/n_i 成线性关系. 因此, 选用介电常数高的衬底材料, 适当提高MoS₂系统的载流子浓度, 同时降低杂质的浓度, 可以有效提高MoS₂系统的迁移率. 研究结果为探索以MoS₂为基础的新型纳米光电器件的研究和实际应用提供了理论依据. 关键词： 二硫化钼 迁移率 电输运 平衡方程     

(Cu,N)共掺杂TiO2/MoS2异质结的电子和光学性能:杂化泛函HSE06

在密度泛函理论的基础上,系统地研究了Cu/N（共）掺杂的TiO₂/MoS₂异质结体系的几何结构、电子结构和光学性质.计算发现,TiO₂/MoS₂异质结的带隙相比于纯的TiO₂（101）表面明显变小,Cu/N（共）掺杂TiO₂/MoS₂异质结体系的禁带宽度也明显地减小,这导致光子激发能量的降低和光吸收能力的提高.通过计算Cu/N（共）掺杂TiO₂/MoS₂的差分电荷密度,发现光生电子与空穴积累在掺杂后的TiO₂（101）表面和单层MoS₂之间,这表明掺杂杂质体系可以有效地抑制光生电子-空穴对的复合.此外,我们计算了在不同压力下TiO₂/MoS₂异质结的几何、电子和光学性质,发现适当增加压力可以有效提高异质结的光吸收性能.本文结果表明,Cu/N（共）掺杂TiO₂/MoS₂异质结和对TiO₂/MoS₂异质结加压都能有效地提高材料的光学性能.     

Si改性MoS2对g3环保气体典型分解组分的吸附特性研究

g3(green gas for gird)环保气体(C₄F₇N/CO₂混合)作为SF₆最具潜力的新型环保绝缘替代气体,近几年来受到了广泛关注.通过分析g3气体绝缘组合开关设备中的分解组分来检测局部放电、过热等缺陷故障,对于电力设备运行状态的评估和诊断具有重要作用.本文提出利用Si原子掺杂改性来提高MoS₂的气敏和吸附性能,并基于密度泛函理论(DFT)的计算方法,通过吸附能、电荷转移、态密度和局部态密度等参数指标,探究了本征MoS₂、Si改性MoS₂(Si-MoS₂)对g3气体典型分解组分—COF₂、CF₄、CF₃CN的吸附气敏机理.分析表明Si原子在MoS₂表面具有稳定的掺杂结构,相比本征MoS₂,Si原子改性之后的MoS₂的导电性得到了有效增强;Si-MoS₂     

常压CVD法合成铌掺杂少层MoS2

利用粉体NbCl₅作为Nb掺杂源,采用常压CVD方法合成了大尺寸Nb掺杂的少层MoS₂薄膜。通过扫描电子显微镜和原子力显微镜观察获得了该薄膜样品的形貌和厚度信息。拉曼光谱和X射线光电子谱测试证实了Nb被掺入到了MoS₂薄膜中,Nb掺杂的MoS₂合金薄膜已经形成。最后,对Nb掺杂的少层MoS₂薄膜的电学性质进行了测试。     

单层二硫化钼的制备及在器件应用方面的研究

二硫化钼(MoS₂)作为一种新兴的二维半导体材料,它具有天然原子级的厚度以及优异的光电特性和机械性能,在未来超大规模集成电路中具有巨大的应用潜力.本文综述了我们课题组在过去几年中在单层MoS₂薄膜研究方面所取得的进展,具体包括:在MoS₂薄膜制备方面,通过氧辅助气相沉积方法,实现了大尺寸MoS₂单晶的可控生长;通过独特的多源立式生长方法,实现了4 in晶圆级大晶粒高定向的单层MoS₂薄膜的外延生长,样品显示出极高的光学和电学质量,是目前国际上报道的质量最好的晶圆级MoS₂样品;通过调节MoS₂薄膜的氧掺杂浓度,可以实现对其电学和光学特性的有效调控.在MoS₂薄膜器件与应用方面,利用制备的高质量单层MoS₂薄膜,实现了高性能柔性晶体管的集成,这种大面积柔性逻辑和存储器件显示出优异的电学性能;在集成多层场效应晶体管的基础上,设计,加工了垂直集成的多层全二维材料的多功能器件,充分发挥器件的组合性能...     

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The MoS₂ self-lubrication coating spraying in the surface of 316LN austenitic stainless steel was developed and investigated. The test result shows that the coating had the preferable friction properties at liquid nitrogen temperatures (77K) for high pressure, and the bonding strength test showed that the coating was good adhesion with base materials. In addition, after the thermal shock between 300K and 77K, The coating was free from cracks, flakes and debonding. The average friction coefficient of MoS2 coating under static compression was reported, which indicated that the friction coefficient was less than 0.1, which met the requirements of ITER.     

Composite ceramic-Ni60 coating fabricated via supersonic plasma spraying

Using the supersonic plasma spraying (SPS) technique, a composite ceramic-Ni60 coating was prepared on a 45# steel substrate. The particle morphology, coating morphology, and phase structure of the coating were analyzed via scanning electron microscopy and X-ray diffraction. Moreover, the tribological properties of the coating were determined via friction and wear experiments. The results revealed that: the crystal structure of the SPS-produced coating is composed of six phase-structure types, and the coating structure was dense with low porosity. During the wear test (rotation speed of ball: 300 rpm, load: 50 N), the friction coefficient decreased by 32.75%, and the coating underwent abrasive wear (wear mechanism).     

XPS investigation of preferential sputtering of S from MoS2 and determination of MoSx stoichiometry from Mo and S peak positions

The preferential sputtering of S from bulk MoS₂ standard samples exposed to 3 keV Ar⁺ ion bombardment has been studied by XPS. The MoS_x stoichiometry decreases from MoS₂ to MoS_1.12 with a concomitant reduction in the Mo 3d_5/2 binding energy from 229.25 to 228.35 eV. The altered layer extends to a depth of 3.8 nm and is proposed to consist of a single amorphous MoS_x phase in which Mo has a varying number of nearest neighbour S atoms. Using peak positions alone it is possible to determine the MoS_x stoichiometry to an accuracy of x±0.1 from a plot of MoS_x stoichiometry against (Mo 3d_5/2–S 2p_3/2) binding energy. The results are of strong current interest for coating analysis applications as MoS₂ is a compound capable of providing low friction properties when incorporated into hard coatings.     

Microstructure and tribological properties of TiCu2Al intermetallic compound coating

TiCu₂Al ternary intermetallic compound coating has been in situ synthesized successfully on pure Ti substrate by laser cladding. Tribological properties of the prepared TiCu₂Al intermetallic compound coating were systematically evaluated. It was found that the friction coefficient and wear rate was closely related to the normal load and sliding speed, i.e., the friction coefficient of the prepared TiCu₂Al intermetallic compound coating decreased with increasing normal load and sliding speed. The wear rate of the TiCu₂Al intermetallic compound coating decreased rapidly with increasing sliding speed, while the wear rate first increased and then decreased at normal load from 5 to 15 N.     

基于滑动势能面的二维材料原子尺度摩擦行为的量化计算

近年来,二维材料优异的摩擦特性成为人们关注的焦点,然而目前缺乏理论上对其摩擦力进行快速、有效、精确的计算预测方法.本文提出采用密度泛函理论计算真实体系的滑动势能面,利用得到的"数值型势能面"替代传统的解析势函数,并结合Prandtl-Tomlinson模型,量化求解具有复杂形状势能面的真实二维材料体系的摩擦行为.基于该方法,揭示了原子力显微镜实验中观察到的石墨烯Moire纹超晶格结构的双周期"黏-滑"摩擦现象;理论预测了二维材料异质结构的层间超低摩擦现象,相对于同质材料,其静摩擦力和滑动摩擦力均成数量级降低,发现势能面起伏和驱动弹簧刚度均会影响层间相对滑动路径,进而对层间的摩擦行为产生影响.该方法同样可拓展到其他van der Waals作用主导的界面摩擦体系.     

Electronic and optical properties of 3N-doped graphdiyne/MoS2 heterostructures tuned by biaxial strain and external electric field

The construction of van der Waals (vdW) heterostructures by stacking different two-dimensional layered materials have been recognised as an effective strategy to obtain the desired properties. The 3N-doped graphdiyne (N-GY) has been successfully synthesized in the laboratory. It could be assembled into a supercapacitor and can be used for tensile energy storage. However, the flat band and wide forbidden bands could hinder its application of N-GY layer in optoelectronic and nanoelectronic devices. In order to extend the application of N-GY layer in electronic devices, MoS₂ was selected to construct an N-GY/MoS₂ heterostructure due to its good electronic and optical properties. The N-GY/MoS₂ heterostructure has an optical absorption range from the visible to ultraviolet with a absorption coefficient of 10⁵ cm^-1. The N-GY/MoS₂ heterostructure exhibits a type-Ⅱ band alignment allows the electron-hole to be located on N-GY and MoS₂ respectively, which can further reduce the electron-hole complexation to increase exciton lifetime. The power conversion efficiency of N-GY/MoS₂ heterostructure is up to 17.77%, indicating it is a promising candidate material for solar cells. In addition, the external electric field and biaxial strain could effectively tune the electronic structure. Our results provide a theoretical support for the design and application of N-GY/MoS₂ vdW heterostructures in semiconductor sensors and photovoltaic devices.     

一种简单的化学气相沉积法制备大尺寸单层二硫化钼

最近单层二硫化钼以其直接带隙的性质及在电子器件、催化、光电等领域中的潜在应用而备受关注.化学气相沉积法能够制备出高质量、大尺寸且性能优良的单层二硫化钼,但其制备工艺比较复杂.本文采用简化的化学气相沉积法在蓝宝石衬底上制备出了大尺寸的单晶二硫化钼.清洗衬底时,只需要简单的清洁,不需要用丙酮、食人鱼溶液(H_2SO_4/H_2O_2=3:1)等处理,这样既减少了操作步骤,又避免了潜在的危险.升温时直接从室温加热到生长的温度,不必分段升温,并且采用常压化学气相沉积法,不需要抽真空等过程,使得实验可以快捷方便地进行.光学显微镜、拉曼光谱和光致发光谱的结果表明,生长的二硫化钼为规则的三角形单层,边长为50μm左右,远大于机械剥离的样品.     

层状二硫化钼研究进展

近年来,层状二硫化钼由于其特殊的类石墨烯结构和独特的物理化学性质已成为国内外研究的热点.本文综述了层状二硫化钼的物理结构、价带结构和光学性质;介绍了制备方法,包括生长制备和剥离制备.生长制备的原料包括四硫代钼酸铵((NH4)_2MoS_4)、钼(Mo)和三氧化钼(MoO_3)等.剥离制备包括微机械剥离、液相超声法、锂离子插层法和电化学锂离子插层法等.归纳了层状二硫化钼在场效应晶体管、传感器和存储方面的应用,展望了层状二硫化钼的研究前景.