Conductance studies of some ammonium and alkali metal salts in propylene carbonate

Conductance data are reported for NaI, KI, RbI, CsI, NH₄I, NaClO₄, and KClO₄ in propylene carbonate at 25°C in the concentration range 1×10^–4 –8.3×10^–3M. Analysis of the data with the current conductance theories indicates negligible ion-association, strong cation-solvent and weak anion-solvent interactions.     

扫描离子电导显微镜的原理及应用

扫描离子电导显微镜(SICM)是一种扫描探针显微技术,通过测定超微玻璃管探针的离子电流,它能够非接触地扫描样品表面,进而研究样品的形貌及性质。SICM具有成像分辨率高、探针易于制备和对被成像物体无损伤等特点,特别适用于研究生理条件下的活体细胞,是一种与扫描电化学显微镜及原子力显微镜互补的扫描探针显微镜技术。SICM能够对软界面及表面,如活细胞表面的显微结构,进行高分辨率成像;并能够与其它技术联用,研究细胞形貌与功能的关系;还能控制沉积特定分子,实现纳米尺度的显微操作与加工。本文对SICM的发展历史、仪器构造、基本原理及应用进行了综述。     

Effect of CuO addition on the optical and electrical properties of sodium zinc borophosphate glasses

Sodium borophosphate glasses doped with copper ions having general composition 20Na₂O-20ZnO-25B₂O₃-(35-x) P₂O₅-x CuO (x=1-8 mol %) were prepared using conventional melt-quench method and characterized by density, UV-visible optical absorption, photoluminescence and conductivity measurements. E_optical values for different glass samples are found to decrease systematically from 3.5 to 2.5 eV with increase in CuO content in the glass. Network modifying action of CuO with the glass network has been confirmed from the UV-visible optical absorption studies. Presence of Copper in the form of Cu⁺ species has been confirmed from photoluminescence measurements. The electrical conductivity (σ) increases with increase in copper oxide content in the glass and temperature dependence of electrical conductivity confirmed the semiconducting nature of the samples.     

C20分子的一个电子输运模型研究

本文构建了Li链为电极的富勒烯C20分子的电子输运模型, 使用非平衡格林函数方法(Non-equilibrium Green's function, NEGF)对构建的Li电极和C20分子构成的分子器件进行了电子输运性质的计算. 计算得出了电子透射谱和电流电压曲线, 分析了产生这个分子器件电子输运性质的原因. 研究计算结果发现,大部分能量的电子是不会穿过器件的, 即使考虑不同偏压,能穿过器件的电子都集中在几个固定的能量上, 且在这几个固定能量上透过率比较高. 计算得出的伏安曲线说明在偏压为1.925V时电流达到最大, 只有在这个偏压周围才有相对明显的电流.     

Single-molecule conductance measurement of self-assembled organic monolayers using scanning tunneling spectroscopy in combination with statistics analysis

Based on ambient atmosphere scanning tunneling microscope (STM) technique, scanning tunneling spectroscopy (STS) combined with statistics analysis was developed to investigate the single-molecule conductance of various kinds of molecules which were self-assembled on the Au (1 1 1). Conductance histograms obtained from current-voltage curves revealed well-defined peaks at integer multiples of a fundamental conductance and were used to identify the conductance of a single molecule. The conductances of saturated molecules like 1,8-octanedithol and hexanethiocyanate were found to be 0.072 × 10⁻⁴G₀ and 0.06 × 10⁻⁴G₀ respectively and 0.23 × 10⁻⁴G₀ and 0.13 × 10⁻⁴G₀ for unsaturated molecules like 5,5′-dithiol- 2,2′,5′,2″-terthiophene and 4,4′-dithio-tert(phenylene ethylene).     

电导法研究树脂与游离酸的相互作用

利用电导实验技术跟踪树脂吸附游离酸的行为 ,讨论了外加盐和乙醇等因素对吸附的影响 ,利用固 -液相互作用方程求取吸附剂 -吸附质相互作用能。实验结果表明 ,树脂吸附游离酸 ,其表观吸附速率常数随着外加盐离子浓度的增大而减少 ;表观吸附速率常数与吸附剂 -吸附质相互作用能存在线性关系。     

Metal nanowires fabricated by means of magnetostrictive actuator

A new method of fabricating nanowires for electric conductance quantization studies is proposed as an alternative to the method based on converse piezoelectric effect. Commonly used for nanowire fabrication, piezoelectric actuators are expensive and require high-level voltage control signal. The method presented in this paper is based on the use of magnetostrictive actuator. Both the actuator structure and the method of the conversion factor measurement are discussed. The results of the tests of the magnetostrictive actuator are also reported. The parameters of the proposed actuator are compared with those of its piezoelectric counterpart used to date. The results of measurement confirm that the proposed actuator can be used for studying electric conductance quantization in nanowires. Presented at the X-th Symposium on Surface Physics, Prague, Czech Republic, July 11–15, 2005     

Micro-thermal analysis of thermal conductance distribution in advanced silicon nitrides

A micro-thermal analysis technique was applied to investigate advanced silicon nitride materials, which exhibit high thermal conductivity. Local thermal properties in the microstructure were evaluated, and the grain boundaries were observed to have lower thermal conductance than the Si₃N₄ grains. It was found that thermal conductance both in the grains and boundaries was lowered by the addition of the sintering aid Al₂O₃, which is soluble in Si₃N₄ grains. This indicates that high thermal conductivity in silicon nitride ceramics is achieved both by grain growth, leading to a reduction in boundary density, and by eliminating soluble elements in silicon nitride grains. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanical fabrication of metal nano-contacts showing conductance quantization under electrochemical potential control

We have mechanically fabricated Ni and Cu nano-constrictions in solution to study their quantized conductance behavior under electrochemical potential control. Conductance quantization was observed at both metals in solution at room temperature for the first time. The conductance of Cu nano-constriction was quantized in units of G₀(=2e²/h). A sharp 1G₀ peak was observed in the conductance histogram. For Ni, a rather broad peak at 1–1.5G₀ was observed in the histogram. The conductance quantization behavior was discussed by comparing previously documented results of nano-constrictions fabricated in air or ultra-high vacuum conditions, with those fabricated in solution.