Direct visualization of structural defects in 2D semiconductors

Direct visualization of the structural defects in two-dimensional (2D) semiconductors at a large scale plays a significant role in understanding their electrical/optical/magnetic properties, but is challenging. Although traditional atomic resolution imaging techniques, such as transmission electron microscopy and scanning tunneling microscopy, can directly image the structural defects, they provide only local-scale information and require complex setups. Here, we develop a simple, non-invasive wet etching method to directly visualize the structural defects in 2D semiconductors at a large scale, including both point defects and grain boundaries. Utilizing this method, we extract successfully the defects density in several different types of monolayer molybdenum disulfide samples, providing key insights into the device functions. Furthermore, the etching method we developed is anisotropic and tunable, opening up opportunities to obtain exotic edge states on demand.     

Curie温度附近稀磁半导体(Ga,Mn)As的电学噪声谱性质

建立了自发噪声谱测量系统来研究稀磁半导体（Ga,Mn）As的电学噪声性质.通过测量（Ga,Mn）As材料的自发噪声谱,发现（Ga,Mn）As的自发涨落会随温度升高而逐渐增大,同时,外加磁场会降低（Ga,Mn）As的自发涨落,这来源于外加磁场导致的（Ga,Mn）As磁畴部分有序化.此外,不同频率的噪声随温度的变化规律有很大差异：当频率低于30 kHz的时候,噪声谱和温度的变化关系和热噪声很相似,但数值上明显大于热噪声的值;当频率在30 kHz左右的时候,噪声大小和温度成线性关系;当频率大于30 kHz以后,在相变点附近噪声大小和温度的关系出现了明显的转折,高频高温噪声的大小和热噪声的理论值非常接近.这些结果有助于深入理解（Ga,Mn）As磁性起源的物理机制. 关键词： 自旋电子学 稀磁半导体 自发涨落谱     

二硫化钼的电子能带结构和低温输运实验进展

二硫化钼是一种层状的过渡金属硫族化合物半导体,它在二维自旋电子学、谷电子学及光电子学领域有很多的应用.本综述以二硫化钼为代表,系统介绍其单层、双层及转角双层的堆垛和能带结构;介绍了转角双层莫尔超晶格的制备方法、以及低温电学输运方面的实验进展,例如超导和强关联现象;分析了转角过渡金属硫化物莫尔超晶格在优化接触和样品质量等方面存在的一些挑战,并展望该领域未来的发展.     

Cryptanalysis of fair quantum blind signatures

We investigate the fair quantum blind signature scheme proposed by Wang and Wen [Wang T Y and Wen Q Y 2010 Chin.Phys.B 19 060307],which uses the fundamental properties of quantum mechanics and the availability of a trusted arbitrator.However,in this paper,we find that the protocol cannot satisfy the property of non-forgeability even under the condition that the trusted arbitrator is totally credible.Moreover,a simple feasible suggestion for improving the protocol is proposed.     

DMTAQ光度法测定微量镍的研究及应用

早在1888年Traumarn就提出了4-(2-噻唑偶氮)-间苯二酚(TAR)和1-(2-噻唑偶氮)-2-萘酚(TAN)等噻唑偶氮化合物,但并未研究它与金属离子的生色性和在分析上的应用.噻唑偶氮类试剂是继吡啶偶氮类试剂之后发展起来的另一类重要的有前途的显色剂.此类试剂中的基本分析功能团是:由于其中电负性大的氮、氧等原子共同存在并同时参与金属螯合物的形成,从而增强了邻羟基偶氮酚与金属离子的生色作用,提高了显色反应的灵敏度.此类试剂在分析化学中的应用已见诸报道.自Savvin S B于1970年首次合成2-(2-4,     

模糊系统可靠性仿真方法的研究与应用

探讨模糊系统可靠性仿真的方法和实现步骤，为缺乏实验与现场数据资料的新型、复杂装备储存可靠性的研究提供了技术途径。     

Ni/4H-SiC 肖特基势垒磁场下输运性质的分析

采用高真空电子束蒸发的方法将镍 (Ni)淀积在 4H SiC(0 0 0 1)面上 ,制备出良好的Ni/4H SiC肖特基接触 .研究了Ni/4H SiC肖特基势垒在强磁场和低温下的I -V特性 ,并以热电子发射理论为基础 ,结合弛豫近似玻尔兹曼方程对Ni/4H SiC肖特基势垒在磁场下的输运性质进行了分析和计算 ,发现电流的变化与磁场的平方和电压成线性关系 ,和温度成反比关系 ,与实验结果基本符合     

基于区间直觉模糊不确定语言变量的VIKOR方法及其在房地产开发风险评价中的应用

采用区间值直觉模糊不确定语言变量建模决策中存在的不确定信息,给出了一个新的不确定环境下的VIKOR方法.首先采用区间直觉模糊不确定语言变量对方案进行评价,然后将VIKOR方法进行推广到新的不确定环境下,给出新的方案排序方法.最后为了说明方法的有效性和合理性,将所给的方法应用于房地产开发方案的风险评价中.     

Precisely controlling the twist angle of epitaxial MoS2/graphene heterostructure by AFM tip manipulation

Two-dimensional (2D) moiré materials have attracted a lot of attention and opened a new research frontier of twistronics due to their novel physical properties. Although great progress has been achieved, the inability to precisely and reproducibly manipulate the twist angle hinders the further development of twistronics. Here, we demonstrated an atomic force microscope (AFM) tip manipulation method to control the interlayer twist angle of epitaxial MoS₂/graphene heterostructure with an ultra-high accuracy better than 0.1°. Furthermore, conductive AFM and spectroscopic characterizations were conducted to show the effects of the twist angle on moiré pattern wavelength, phonons and excitons. Our work provides a technique to precisely control the twist angle of 2D moiré materials, enabling the possibility to establish the phase diagrams of moiré physics with twist angle.     

酸化沉淀蛋白-超快速液相色谱-串联质谱法测定肝损伤大鼠血浆中的头孢呋辛

为了研究二代头孢类新药头孢呋辛赖氨酸在肝损伤大鼠体内的药代动力学过程,建立了采用超快速液相色谱-串联质谱(UFLC-MS/MS)快速测定肝损伤模型大鼠血浆中头孢呋辛含量的方法。血浆样品在酸性条件下用乙腈沉淀蛋白,采用Shim-pack XR-ODS色谱柱(75 mm×3.0 mm, 2.2 μm)为分析柱、乙腈-0.1%甲酸水溶液(40:60, v/v)为流动相、流速为400 μL/min进行色谱分离,采用电喷雾负离子(ESI~)模式电离、多反应监测(MRM)模式进行质谱检测,用于定量分析的离子对分别为m/z 423.2→206.8 (头孢呋辛)和m/z 454.1→238.4 (内标头孢噻肟)。结果表明,大鼠血浆中头孢呋辛的质量浓度在0.01～1 mg/L和1～400 mg/L范围内线性关系良好(r＞0.99),定量限为0.01 mg/L,日内和日间精密度(以相对标准偏差(RSD)计)均小于11.5%,准确度(RE)为~7.1%～2.2%,平均萃取回收率大于83.5%,样品运行时间仅为3.0 min,能够满足生物样品的测定需求。该法简便、快速,已用于肝损伤大鼠静脉注射头孢呋辛赖氨酸的药代动力学预实验研究。