介稳态TiCl4醇水溶液水解制备TiO2致密层及其在无机-有机杂化异质结钙钛矿太阳电池中的应用

致密层作为钙钛矿太阳电池的重要组成部分, 对其制备方法, 工艺及微结构等性质的研究对提高钙钛矿太阳电池的光伏性能具有重要影响. 本文利用介稳态的TiCl₄醇水溶液作为前驱体溶液, 通过旋涂水解制备TiO₂致密层, 并研究了前驱体溶液不同醇水比对致密层微结构及其相应太阳电池光伏性能的影响. 结果表明, 将2 mol.L_-1的TiCl₄的水溶液按醇水体积比3:1的比例用异丙醇稀释后所制备的TiO₂致密层其厚度为126 nm, 且相应的太阳电池取得最高的光电转换效率10.6 %.     

基于 InSe/MoTe2 异质结构的超灵敏宽光谱光电探测器

基于光栅效应的二维材料垂直结构可实现高灵敏度和宽光谱光探测器。本文报告了一种基于硒化铟（InSe）/二碲化钼（MoTe₂）垂直异质结构的高灵敏度光电探测器,该探测器在 365~965 nm 波长范围内具有出色的宽光谱探测能力。顶层的InSe用作调节沟道电流的光栅层,MoTe₂ 则用作传输层。通过结合两种材料的优势,该光电探测器的响应时间为 21.6 ms,比探测率在365 nm光照下可以达到1.05×10¹³ Jones,在965nm光照下也可达到10⁹ Jones数量级。外量子效率可达 1.03×10⁵%,显示出强大的光电转换能力。     

单层硫化钼的研究进展

单层硫化钼(MoS2)是具有直接帯隙1.8 eV的二维半导体,因其特殊的六方晶系层状结构,而具有优异的物理和化学性质。简要介绍了MoS2材料的几种主要制备方法:如高温硫化法、水热法以及表面活性剂促助法等,讨论了各种制备方法在国内外的研究现状及优缺点。给出了单层MoS2在晶体管、集成电路、逻辑运算等方面的一些应用。与硅晶体管相比其晶体管体积更小、更省电,并可减少短通道效应,电流开/关比例高于1010。这些应用说明了其可被广泛应用于未来的纳米电子器件。最后,对MoS2未来的发展方向进行了展望,认为工艺制备方法有待进一步改善,单层MoS2的应用领域也有待进一步深入拓展。     

二硫化钼薄膜的制备和性质研究

基于第一性原理,应用Materials Studio软件对2H-MoS2的能带结构、态密度、光学特性等进行了模拟研究.结果 表明:MoS2是间接带隙半导体,禁带宽度约为1.1275 eV;材料在紫外至可见光波段具有一定吸收,吸收系数随波长增加而减小,拉曼光谱在375和400 cm-1分别出现了E2g1和A1g两个振动模式.在39.5°,33.5°等位置处出现了(103),(101)等晶面的衍射峰.采用磁控溅射的方法,在石英衬底上制备了不同厚度的MoS2薄膜,发现该薄膜具有(101)择优取向,在375和407 cm-1处也分别出现了E2g1和A1g两个拉曼峰.随着厚度的增加,薄膜在可见光波段透过率下降,光学带隙向长波长移动,模拟结果与实验结果基本吻合.     

Manganese and chromium doping in atomically thin MoS2

Recently, two-dimensional materials have been attracting increasing attention because of their novel properties and promising applications. However, the impurity doping remains a significant challenge owing to the lack of the doping strategy in the atomically thin layers. Here we report on the chromium (Cr) and manganese (Mn) doping in atomically-thin MoS₂ crystals grown by chemical vapor deposition. The Cr/Mn doped MoS₂ samples are characterized by a peak at 1.76 and 1.79 eV in photoluminescence spectra, respectively, compared with the undoped one at 1.85 eV. The field-effect transistor (FET) devices based on the Mn doping show a higher threshold voltage than that of the pure MoS₂ while the Cr doping exhibits the opposite behavior. Importantly, the carrier concentration in these samples displays a remarkable difference arising from the doping effect, consistent with the evolution of the FET performance. The temperature-dependent conductivity measurements further demonstrate a large variation in activation energy. The successful incorporation of the Mn and Cr impurities into the monolayer MoS₂ paves the way towards the high Curie temperature two-dimensional dilute magnetic semiconductors.     

高k HfLaO栅介质MoS2晶体管的性能研究

比较研究了HfO₂与HfLaO栅介质多层MoS₂场效应晶体管。实验结果表明,与HfO₂栅介质MoS₂晶体管相比,HfLaO栅介质MoS₂晶体管表现出更优的电性能。电流开关比高达1×10⁸,亚阈斜率低至76 mV/dec,界面态密度低至1.1×10¹² cm-2·eV-1,载流子场效应迁移率高达1×10⁹ cm²·V-1·s-1。性能改善的原因在于镧(La)对HfO₂的掺杂形成HfLaO化合物,减小栅介质薄膜的表面粗糙度,降低缺陷电荷密度,改善了栅介质/沟道界面特性,从而减小了界面态密度,抑制了库仑散射和界面粗糙散射。最终,提高了多层MoS₂晶体管的场效应迁移率,改善了晶体管的亚阈特性。     

Theoretical study of defect impact on two-dimensional MoS2

Our theoretical findings demonstrate for the first time a possibility of band-gap engineering of monolayer MoS₂ crystals by oxygen and the presence of vacancies. Oxygen atoms are revealed to substitute sulfur ones, forming stable MoS_2-xO_x ternary compounds, or adsorb on top of the sulfur atoms. The substituting oxygen provides a decrease of the band gap from 1.86 to 1.64 eV and transforms the material from a direct-gap to an indirect-gap semiconductor. The surface adsorbed oxygen atoms decrease the band gap up to 0.98 eV depending on their location tending to the metallic character of the electron energy bands at a high concentration of the adsorbed atoms. Oxygen plasma processing is proposed as an effective technology for such band-gap modifications.     

单层二硫化钼的磁光电导率研究

考虑外加磁场导致的量子化朗道能级以及邻近效应诱导产生的交换作用,采用无规相近似(Random-phase approximation,RPA)下的介电函数对单层二硫化钼(Monolayer molybdenum disulfide,ML-MoS₂)的纵向磁光电导率进行理论研究。探究了磁场、邻近效应诱导产生的交换作用等因素对纵向磁光电导率的影响。在太赫兹(Terahertz,THz)频段,可以看到由导带内电子跃迁所贡献的两个磁光吸收峰。在可见光频段,可以观察到从价带到导带电子跃迁所贡献的多个磁光吸收峰。研究结果表明,邻近效应诱导产生的交换作用和磁场强度对纵向磁光电导率有重要的影响,单层二硫化钼可应用于可见光到太赫兹频段的自旋电子学和谷电子学磁光器件。     

Simulation of MoS2 stacked nanosheet field effect transistor

Transition metal dichalcogenides are nowadays appealing to researchers for their excellent electronic properties. Vertical stacked nanosheet FET (NSFET) based on MoS₂ are proposed and studied by Poisson equation solver coupled with semi-classical quantum correction model implemented in Sentaurus workbench. It is found that, the 2D stacked NSFET can largely suppress short channel effects with improved subthreshold swing and drain induced barrier lowering, due to the excellent electrostatics of 2D MoS₂. In addition, small-signal capacitance is extracted and analyzed. The MoS₂ based NSFET shows great potential to enable next generation electronics.     

Growth of Fe-Doped and V-Doped MoS2 and Their Magnetic-Electrical Effects

Magnetism in two-dimensional (2D) materials has attracted much attention recently. However, intrinsic magnetic 2D materials are rare and mostly unstable in ambient. Although heteroatom doping can introduce magnetism, the basic property especially the electrical-magnetic coupling property has been rarely revealed. Herein, both iron (Fe)-doped and vanadium (V)-doped MoS₂ films were grown by chemical vapor deposition. Through studying the structure and electrical property of Fe-doped and V-doped MoS₂, it was found that both Fe and V doping would decrease the electron concentration, exhibiting a p-type doping effect. Significantly, V-doped MoS₂ displays a p-type conduction behavior. Although the carrier mobility decreases after heteroatom doping, both Fe and V doping could endow MoS₂ with magnetism, in which the transfer curves of both MoS₂ transistors exhibit a strong magnetic-dependent behavior. It is found that the magnetic response of Fe-doped MoS₂ can be tuned from ~0.2 nA/T to ~1.3 nA/T, with the tunability much larger than that of V-doped MoS₂. At last, the magnetic mechanism is discussed with the local magnetic property performed by magnetic force microscopy. The typical morphology-independent magnetic signal demonstrates the formed magnetic domain structure in Fe-doped MoS₂. This study opens new potential to design novel magnetic-electrical devices.     

MoS2/WSe2-PVA薄膜热光全光调制器(特邀)

全光调制器在全光信号处理和通信等全光应用中起着重要的作用。主要研究了基于MoS2-PVA薄膜实现的全光调制器。此外,也验证了WSe2-PVA薄膜也可实现全光调制。该器件利用热光效应,结合偏振干涉实现了全光调制,得到了长时间稳定输出的调制信号。将980 nm的脉冲信号作为控制光,MoS2或WSe2吸收光产生热量,使薄膜的折射率发生改变,从而改变1 550 nm信号光的偏振态,实现980 nm控制光对1 550 nm光的调制。得到的MoS2-PVA薄膜全光调制器的上升沿时间为526 s。