DNA分子材料电子输运研究进展

由于DNA分子在纳米电子学、分子电子学中具有广泛的潜在应用,对DNA分子中电子输运特性的研究备受关注.然而,目前对DNA分子电子输运特性的研究还未形成统一认识.阐述了DNA分子中的电子输运理论、实验研究进展.实验方面,DNA分子呈现出绝缘体、半导体、导体的各种可能结果都有报道;理论方面,主要形成了2种方法,一种是第一原理计算,另一种是基于哈密顿量模型的计算.     

具有边缘缺陷石墨烯纳米结的自旋输运特性(英文)

利用第一性原理研究了两种具有边缘缺陷石墨烯纳米结的自旋输运,即边界氢原子饱和和未被饱和两种情况。结果表明:边缘缺陷改变了电子的输运行为。对于完整的石墨烯纳米带,两种自旋的电子在费米能级附近是完全简并的;对于含有边缘缺陷的石墨烯纳米结,两种自旋的电子在费米能级附近的很大能量范围内表现出自旋分离。电子局域态密度可进一步说明这种输运行为。这些纳米结可产生与自旋相关的极化电流。特别对于未饱和的缺陷结,在任何偏压下都有较高的自旋滤波效率。     

表面声波单电子输运器件中弱电流的测量

研究表面声波单电子输运（SAW/SET）器件中的量子化声电电流对于揭示表面声波驱动的单电子输运特性有重要意义,并且有可能应用于最子电流基准,从而把安培与基本电荷和频率联系起来。为此设计了一种高精度高智能测量系统用于测量表面声波单电子输运器件中的声电电流。通过采用高性能I—V转换器和小波去噪等措施,使系统的噪声峰峰值小于30fA;采用LabVIEW编写的测量程序和合适的硬件实现了智能化的自动测量。该系统已成功地应用到SAW／SET器件中弱电流的测量,为将来揭示表面声波驱动的单电子输运特性和量子电流基准的可能实现做了有益的探索。     

芳烃体系分子导线的理论研究

在第一性原理的基础上,对芳烃体系与金表面形成的分子线的电学特性进行了理论研究,利用密度泛函理论计算了分子及扩展分子的电子结构;定量计算了分子与金表面的相互作用能和电子跃迁谱;利用弹性散射格林函数法研究了分子线的伏-安特性.计算结果表明:HOMO和LUMO间的禁带宽度、π电子数目、分子与金表面的相互作用以及分子轨道的扩展性等因素都将影响电子在分子线内的输运特性.     

声表面波单电子输运器件的频率响应研究

为减少样品盒的电磁效应对声表面波单电子输运的影响,需要优化器件的样品盒结构.我们用全波法模拟不同样品盒的声表面波单电子输运器件的频率响应,同时测试该频率响应.模拟结果与测试结果较为一致.二者表明,电磁馈通效应对声表面波单电子输运器件的频率响应影响显著.通过适当改进器件的样品盒可以较有效地抑制电磁馈通效应.这将有助于提高量子化声电电流的精度.     

边缘裁剪石墨烯纳米带的电子输运性质研究

运用第一性原理的密度泛函理论,结合非平衡格林函数,研究了边缘裁剪对Zigzag石墨纳米带(ZGNRs)的电子结构与输运性能的影响。计算结果表明,对Zigzag石墨纳米带边缘的裁剪显著影响了体系的电子输运性能。其中,边缘裁剪使得金属型石墨纳米带的能隙打开,而且随着结构中的Zigzag边缘长度减少,能隙逐渐增大,使得体系由金属型向半导体型转变;同时,边缘裁剪使Zigzag金属型石墨烯纳米带的输运性能降低,电流-电压呈非线性变化,尤其对于M3体系而言,边缘的裁剪使体系表现出很好的开关特性.     

C60富勒烯分子的电子传输特性

采用扩展的Huckel方法与格林函数方法,分析了双Au电极作用下C60富勒烯分子的电子结构与电子输运特性。研究结果表明,C60富勒烯分子与Au电极“接触”后,其分子轨道能级发生了较大的变化,HOMO、LUMO间的能隙显著减小;C60与Au电极之间的结合既有共价键的成分,又有离子键的成分;C60富勒烯分子的电压-电导率曲线以及伏安曲线表现出了微妙的量子特性。     

合金纳米线电子输运性质的理论计算研究

采用分子动力学模拟纳米管中合金纳米线的结构演化以及纳米线电学特性的变化规律。量子效应导致纳米线的电流电压曲线呈现出非线性特点,且在低电压区会出现电导隙,其宽度是由最高分子占据轨道和最低分子未被占据轨道的差值决定。锡原子的掺杂削弱了原本硅锗合金材料内的电子穿透能力,当锡原子数目占整条纳米线原子数的百分之十甚至更多时,由于库仑阻塞效应,在电流电压曲线图的低电压区,电流随电压的变化甚微;当硅锗锡三者原子比例相同时,纳米线的库仑阻塞效应尤为明显。由于隧穿共振效应,电导随电压的增大出现许多共振峰,并且共振峰的数量也随锡原子比例的增加而增加。     

表面声波单电子输运器件中弱电流的测量

研究表面声波单电子输运(SAW/SET)器件中的量子化声电电流对于揭示表面声波驱动的单电子输运特性有重要意义,并且有可能应用于量子电流基准,从而把安培与基本电荷和频率联系起来.为此设计了一种高精度高智能测量系统用于测量表面声波单电子输运器件中的声电电流.通过采用高性能Ⅰ-Ⅴ转换器和小波去噪等措施,使系统的噪声峰峰值小于30fA;采用LabVIEW编写的测量程序和合适的硬件实现了智能化的自动测量.该系统已成功地应用到SAW/SET器件中弱电流的测量,为将来揭示表面声波驱动的单电子输运特性和量子电流基准的可能实现做了有益的探索.     

Quasi‐Monolayer Black Phosphorus with High Mobility and Air Stability

Black phosphorus (BP) exhibits thickness‐dependent band gap and high electronic mobility. The chemical intercalation of BP with alkali metal has attracted attention recently due to the generation of universal superconductivity regardless of the type of alkali metals. However, both ultrathin BP, as well as alkali metal‐intercalated BP, are highly unstable and corrode rapidly under ambient conditions. This study demonstrates that alkali metal hydride intercalation decouples monolayer to few layers BP from the bulk BP, allowing an optical gap of ≈1.7 eV and an electronic gap of 1.98 eV to be measured by photoluminescence and electron energy loss spectroscopy at the intercalated regions. Raman and transport measurements confirm that chemically intercalated BP exhibits enhanced stability, while maintaining a high hole mobility of up to ≈800 cm² V^?1 s^?1 and on/off ratio exceeding 10³. The use of alkali metal hydrides as intercalants should be applicable to a wide range of layered 2D materials and pave the way for generating highly stable, quasi‐monolayer 2D materials.     

化学气相运输法制备正交黑磷

黑磷(Black phosphorus, BP)以其优异而独特的物理化学性质在能源储存与转换、微纳器件、光/电催化和生物医药等领域展现出良好的应用前景。高质量正交BP前体制备是实现二维BP和零维BP量子点应用的关键。本工作采用无温度梯度的化学气相运输(CVT)法研究了矿化剂组分和比例对BP生长的影响。结果表明, 只有锡(或铅)和碘共存且比例合适时才能制备得到正交BP; 生长BP所需的锡碘质量比w(Sn/I₂)范围较宽, 当w(Sn/I₂)=0.47时制得的BP尺寸为1.2 cm, 且产率高、晶体质量较优。结合BP的成核生长机理可知, 锡和碘都对BP的成核生长具有重要作用; 碘的矿化效果较锡明显, 而足量的锡有利于无温度梯度条件下大尺寸块体BP晶体的合成。w(Sn/I₂)=0.47为本工作中制备BP的最佳砂化剂配比。     

Mechanically Controllable Break Junctions for Molecular Electronics

A mechanically controllable break junction (MCBJ) represents a fundamental technique for the investigation of molecular electronic junctions, especially for the study of the electronic properties of single molecules. With unique advantages, the MCBJ technique has provided substantial insight into charge transport processes in molecules. In this review, the techniques for sample fabrication, operation and the various applications of MCBJs are introduced and the history, challenges and future of MCBJs are discussed.     

Black Phosphorus: Optical Characterization,Properties and Applications

The rise of black phosphorus (BP) as a new family member of two‐dimensional (2D) materials brings new concepts and applications to the field, because of the infrared band gap and anisotropic properties of such materials. Among many excellent properties of BP, the optical property attracts special attention in recent years. Optical methods have been widely and successfully used in characterizing BP, not only to obtain the structural information (such as thickness and crystalline orientation), but also to probe the fundamental properties of BP in terms of the behavior of electrons, phonons, excitons etc. In this Review, a comprehensive understanding about the optical characterization of BP such as Raman, absorption, and photoluminescence is presented. Also, the unique optical properties and applications explored in recent years are reviewed.     

2D Black Phosphorus for Energy Storage and Thermoelectric Applications

Recent progress in the currently available methods of producing black phosphorus bulk and phosphorene are presented. The effective passivation approaches toward improving the air stability of phosphorene are also discussed. Furthermore, the research efforts on the phosphorene and phosphorene‐based materials for potential applications in lithium ion batteries, sodium ion batteries, and thermoelectric devices are summarized and highlighted. Finally, the outlook including challenges and opportunities in these research fields are discussed.     

二维黑磷物理性质及化学稳定性的研究进展

1914年科研工作者首次合成了黑磷的块体形式。在黑磷沉寂了100年之后,2014年人们成功地将其薄化到少层状态,得到了新型二维纳米材料——二维黑磷。它是由磷原子堆叠而成的单一元素的二维层状半导体材料,具有合适的可控直接带隙、高的载流子迁移率、高的漏电流调制率、较高的开关电流比、良好的导电导热能力和明显的平面各向异性等性质,在低维无机半导体领域备受关注。二维黑磷是一种具有众多优异性质的内禀p型材料,但在空气中的不稳定性使得目前还不能分离得到大面积磷烯(即单原子层黑磷)薄膜,这限制了二维黑磷的应用。本文综述了自2014年以来国内外关于二维黑磷的研究进展,系统介绍了二维黑磷的结构、制备与性质,重点归纳了包括电学性质、光学性质、力学性质、热学性质和磁学性质在内的物理性质及化学稳定性。最后总结并展望了二维黑磷作为电子材料的广阔前景。     

Growth of Black Phosphorus Nanobelts and Microbelts

Black phosphorus nanobelts are fabricated with a one‐step solid–liquid–solid reaction method under ambient pressure, where red phosphorus is used as the precursor instead of white phosphorus. The thickness of the as‐fabricated nanobelts ranges from micrometers to tens of nanometers as studied by scanning electron microscopy. Energy dispersive X‐ray spectroscopy and X‐ray diffraction indicate that the nanobelts have the composition and the structure of black phosphorus, transmission electron microscopy reveals a typical layered structure stacked along the b‐axis, and scanning transmission electron microscopy with energy dispersive X‐ray spectroscopy analysis demonstrates the doping of bismuth into the black phosphorus structure. The nanobelt can be directly measured in scanning tunneling microscopy in ambient conditions.     

Solid-State Electron Transport Through Carbon Dots Junctions: The Role of Boron and Phosphorus Doping

Carbon dots (CDs) are a new class of nanoparticles that gained widespread attention recently because of their easy preparation, water solubility, biocompatibility, and bright luminescence, leading to their integration in various applications. Despite their nm-scale and proven electron transfer capabilities, the solid-state electron transport (ETp) across single CDs was never explored. Here, a molecular junction configuration is used to explore the ETp across CDs as a function of their chemical structure using both DC-bias current–voltage and AC-bias impedance measurements. CDs are used with Nitrogen and Sulfur as exogenous atoms and doped with small amounts of Boron and Phosphorous. It is shown that the presence of P and B highly improves the ETp efficiency across the CDs, yet without an indication of a change in the dominant charge carrier. Instead, structural characterizations reveal significant changes in the chemical species across the CDs: the formation of sulfonates and graphitic Nitrogen. Temperature-dependent measurements and normalized differential conductance analysis reveal that the ETp mechanism across the CDs behaves as tunneling, which is common to all CDs used here. The study shows that the conductivity of CDs is on par with that of sophisticated molecular wires, suggesting CDs as new ‘green’ candidates for molecular electronics applications.