Proximity-Induced Superconductivity in New Superstructures on 2H-NbSe_2 Surface

Using scanning tunneling microscopy we observe a stripe phase smoothly interfacing with a triangular 2×2 superstructure on the surface of 2 H-NbSe_2 single crystal. Proximity-induced superconductivity is demonstrated in these new ordered structures by measurements of low-temperature tunneling spectra. The modulation of superconductivity by the reconstruction provides an opportunity to understand the interplay between superconductivity and charge orders.     

Formation of Ordered Silicon Structures on a Graphite Surface

Physics of the Solid State - The possibility of formation of ordered silicon structures, including silicene, on the graphite substrate surface has been studied. The effect of various conditions of...     

Niobium Monoxide Superstructures

JETP Letters - The cubic and orthorhombic models of Nb3O3 and Nb6O6 superstructures of nonstoichiometric niobium monoxide Nb0.75O0.75 with double defects have been proposed for the first time on...     

石墨表面吸附钾系统电子性质的理论研究

基于集团模型电荷自洽的EHT(Extended Hückel Tneory)方法对K在石墨(0001)表面吸附态进行了优化计算.在3种不同的覆盖度(Θ)下,对k-石墨系统的电荷转移量△Q、吸附能△E、态密度PDOS和TDOS、Mulliken集居数和成键性质进行了比较.认同K/石墨吸附系统是石墨插层化合物(GIC)的雏型.并用LMTO方法对KC₈完成电子结构的第一性原理研究,得到与EHT完全一致的结果:K4s-Ca杂化态主要位于低能区域远离费米能级,构成反键轨道其电子转移到费米能级附近K3d-Cπ成键的杂化轨道上.空的3d轨道在目前EHT方法和LMTO方法计算中扮演了关键角色.这与其他文献K-4s态处在EF能级的结果不同,但与早期Fischer(1984),Johnson(1986)XPS,ARUPS的实验结果吻合.     

玻碳电极表面催化性质的薄层光谱电化学研究

电位跃-开路驰豫-薄层光谱电化学方法研究了开路情况下,玻碳电极表面对[Fe(CN)6]4-和[(phen)2Cu]2 体系的自身氧化和还原反应的催化作用,获得各体系的催化反应的表观反应速率常数分别为9.02×10-4L/mol/s和1.44×10-3L/mol/s。玻碳电极开路情况下的氧化还原催化性质的研究尚无文献报道。     

纳米级光滑石墨表面的拉曼光谱表征

石墨微结构的表面一般为原子级光滑或纳米级光滑,是研究表面、界面物理性质的重要基础,对结构超润滑、微机电器件的研究和应用非常重要。为了解石墨微结构表面的状态和性质,其无损表征具有重要意义。通过微加工方法制备出石墨微结构,使用微纳机械手上的针尖推动石墨微结构上部可以得到原子级光滑或纳米级光滑的石墨表面。使用拉曼光谱对获得的石墨表面进行表征。通过与原子力显微镜和电子显微镜的表征结果进行对比发现,拉曼光谱能够准确反映石墨表面的缺陷程度,同时具有非接触、无损和快速的优点。这表明拉曼光谱在纳米级光滑石墨表面的表征中能够提供可靠表征信息,并且检测快速、不破坏样品,为石墨结构超润滑和MEMS器件的后续研究和应用奠定了基础。     

Graphite on graphite

We propose potential geometry for fabrication of the graphite sheets with atomically smooth edges. For such sheets with Bernal stacking, the electron–electron interaction and topology should cause sufficiently high density of states resulting in the high temperature of either spin ordering or superconducting pairing.     

Ar离子溅射生成碳纳米管

用扫描电子显微镜(SEM)和透射电子显微镜(TE),研究了离子溅射石墨表面的形貌特征和结构,证实了碳纳米管可通过溅射原子在表面形貌突起部位沉积生长.     

石墨炉原子吸收法测定地表水中钡

在测定样品中加入适当的基体改进剂并控制工作条件及升温程序，可以快速、方便、准确地用石墨炉原子吸收法测定地表水中钡含量。     

Influence of the Porosity of the Surface of a Graphite Furnace on the Atomization of a Sample

The influence of the wear of a tube graphite furnace and the morphological features of its surface on the formation of an atomic-absorption signal has been investigated. Electron-microscopic and mass-spectrometric investigations have shown that, prior to atomization, copper in the form of elementary metal microparticles is found not only on the surface of the furnace but also in the bulk of its pores. Free atoms are formed as a result of the concurrent processes of atomization of a sample on the surface of the furnace and in the bulk of its pores. The change in the apparent energy of formation of free atoms of metals interacting actively with graphite in the process of atomization and the inflection on their Arrhenius plot have been explained qualitatively.     

Crystallization of Semiconductor Nanorods into Perfectly Faceted Hexagonal Superstructures

Super crystallization of ligand‐capped nanocrystals into defined periodic solids from solution is the definitive demonstration of their self‐organizing properties. To date, this has been mainly limited to spherical nanocrystals where organization emulates atom or molecule packing in regular crystals with the most thermodynamically stable arrangement being eventually preferred. Here, the crystallization of wurtzite CdS nanorods into micrometer‐sized CdS superstructures with regular hexagonal symmetry is demonstrated by fine‐tuning the nanorod dispersibility over time. It is shown that the supercrystals have a long nucleation stage to form monolayer hexagons followed by a relatively faster growth stage both occurring rod by rod (in‐plane) and layer by layer (out of plane). The perfectly symmetrical hexagon shape of the final structure is mapped from the wurtzite crystal structure of each individual nanorod where they pack in side by side and end to end arrangements. These well‐defined superstructures are highly attractive for applications that collectively exploit electronic or optical properties that are synthetically tunable through the size and shape of each nanorod building block.     

Substitutional Body-Centered Cubic Superstructures: Feasibility and Stability Analysis

A stability analysis of classical binary bcc superstructures with one or two long-range order parameters is performed. The feasibility criteria for ordered phases formulated for fcc superstructures are found to apply to bcc superstructures. The feasibility criteria assume that the ordering energy in the first coordination sphere is positive, and the energy range in interaction space where bcc superstructures are stable (stability range) is unlimited.     

The Unoccupied Electronic States of the Ultrathin Diphenylphthalide Films on the Surface of the Highly Oriented Pyrolytic Graphite

Physics of the Solid State - The results of diagnostics of the atomic composition of a diphenylphthalide (DPP) film thermally precipitated in vacuum by the of X-ray photoelectric spectroscopy (XPS)...     

Conditions of Formation of Doping Superstructures at Phase Transitions

Physics of the Solid State - This work is aimed at general analytical representation of the conditions necessary for generation of layered periodic doping superstructures resulting from the...     

Unoccupied Electronic States and Potential Barrier in Films of Substituted Diphenylphthalides on the Surface of Highly Ordered Pyrolytic Graphite

Physics of the Solid State - The results of a study of the unoccupied electronic states of ultrathin films of bis-carboxyphenyl-phthalide (DCA-DPP) and bis-methylphenyl-phthalide (DM-DPP) up to 8...     

Graphite polarizability

The components of the polarizability of graphite, which can be assigned to each atom site, are re-evaluated using optical data and shown to be consistent with those estimated from bond polarizability.     

膨胀石墨的Raman光谱研究

以波长为514.5nm的激光对550-920℃制备的膨胀石墨进行了Raman光谱研究,结果表明:膨胀石墨的Raman光谱与高取向热解石墨基本相同,分别在~1350、~1580、~2445、~2725、~3248和~4300cm-1处出现了相应的Raman位移;其中位于~1350、~2445和~4300cm-1的Raman峰位随着制备温度的不同会发生较大的移动,而不同温度制备的膨胀石墨位于~1580、~2725、~3248cm-1处的三个Ra-man峰位基本接近;~2725 cm-1处的二阶模包含两个分别位于2707和2730cm-1处的Raman峰。膨胀石墨的D模与G模强度比ID/IG随着温度升高下降,而D线的二阶模D*峰强ID*与IG的比值ID*/IG的大体变化趋势是随着温度升高而增大。