剪切形变下掺杂及缺陷对MoS2电子结构的影响

本文利用密度泛函理论,研究剪切形变下掺杂改性及不同类型缺陷对MoS2电子结构的影响。发现：剪切形变下,MoS2+P体系为相对最稳定的结构,掺杂改性相较于缺陷对模型稳定性影响更小;模型MoS2+P+Se中P-Mo键易形成共价键,而其中的Se-Mo键和MoS2+P-Mo-S模型中的P-Mo键,易形成离子键;掺杂使MoS2模型能隙变大,而缺陷使能隙减小,且S和Mo原子共缺陷的模型带隙为0;缺陷相较于掺杂改性模型,更能使Mo原子周围增加电荷聚集度,带隙值更低,更能影响或调控模型的电子结构。     

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.     

Identification and elimination of inductively coupled plasma-induced defects in AlxGa1 - xN/GaN heterostructures

By using temperature-dependent Hall,variable-frequency capacitance-voltage and cathodoluminescence (CL) measurements,the identification of inductively coupled plasma (ICP)-induced defect states around the Al x Ga 1-x N/GaN heterointerface and their elimination by subsequent annealing in Al x Ga 1-x N/GaN heterostructures are systematically investigated.The energy levels of interface states with activation energies in a range from 0.211 to 0.253 eV below the conduction band of GaN are observed.The interface state density after the ICP-etching process is as high as 2.75×10 12 cm 2 ·eV 1.The ICP-induced interface states could be reduced by two orders of magnitude by subsequent annealing in N 2 ambient.The CL studies indicate that the ICP-induced defects should be Ga-vacancy related.     

新题征展(69)

A 题组新编 1.已知ABCD为空间四边形,分别求下列情况下两对角线AC、BD所成的角:     

由正交表变换得到的2阶平衡的相关免疫函数

本本文给出了一种运用正交表变换来得到2阶相关免疫函数的特征矩阵的新方法,构造出10个不同的(8,4,2,2)特征矩阵,得到了几个相关结论。     

Gd替代对La0.6-xGdxSr1.4MnO4磁性和输运性质的影响

随着x的增加，多晶La0.6-xGdxSr1.4MnO4（x=0, 0.1, 0.2, 0.4, 0.6）的零场冷却 曲线从类自旋玻璃型转变成顺磁型，并且每条零场冷却 曲线都有一在20K的拐点。这一行为可以从Gd和Mn各自对材料总磁性的不同贡献来理解。另外，在所有的样品中，从100K到室温，都观察到了热激活导电行为。由于Mn-Mn间强的反铁磁耦和，直到外场达到50 kOe，都没有观察到明显的磁电阻效应。     

二元Baskakov算子的一致逼近

Baskakov算子也是一类很重要的正线性算子，在其它领域(如概率及其它学科)都应用很广，本文利用多元分解技巧和已有的一元的结论得出多元Baskakov算子的等价一致逼近定理．     

综合题新编选登

题 1 2 7　过点 (0 ,1)的直线l与曲线C :y =x+1x (x >0 )交于相异两点 ,设曲线C在这两点处的切线分别为l1与l2 ,求l1与l2 交点的轨迹 .解　设直线l与曲线C交于点M (x1,y1) ,N(x2 ,y2 ) ,l1与l2 交于点P(x ,y) ,直线l的斜率为k ,方程为 y =kx +1.对 y =x +1x求导 ,得 :y′ =1- 1x2 .则 y′|x =x1=1- 1x21,y′|x =x2 =1- 1x21.故直线l1的方程为y - (x1+1x1) =(1- 1x12 ) (x -x1) ,即 y =(1- 1x12 )x +2x1(1)同理 ,可求得l2 的方程为y =(1- 1x22 )x +2x2(2 )(1) - (2 )得 (1x22 - 1x12 )x +2x1- 2x2=0 .由于x1≠x2 ,解得x =2x1x2x1+x2(3)由 …     

表面活性剂增敏光度法测定锌

在弱酸性(pH=4.5)介质中,非离子表面活性剂Tween-80存在下,7-(苯并噻唑-2-偶氮)-8-羟基喹啉-5-磺酸(BTAQS)与锌形成2:1的紫色配合物,最大吸收波长位于580nm处,表观摩尔吸光系数为7.4×104L·mol-1·cm-1,锌含量在0-6μg/25mL范围内符合比耳定律。测定矿样中的锌,结果满意。