Electron Transport and Redox Reactions in Molecular Electronic Junctions

Electron transport through single molecules or collections of molecules oriented in parallel can occur by several mechanisms, including coherent tunneling, activated transfer between potential wells, various “hopping” modes, etc. Given suitable energy levels and sufficiently long charge transport times, reduction or oxidation with accompanying nuclear reorganization can occur to generate “polarons”, that is, localized redox centers in the molecule or monolayer. Redox events in molecular junctions are amenable to spectroscopic monitoring in working devices, and can have major effects on the electronic behavior of the junction. Several examples are presented, along with a possible application to molecular memory.     

A Zinc Phthalocyanine Based Periodic Mesoporous Organosilica Exhibiting Charge Transfer to Fullerenes

Periodic mesoporous organosilica (PMO) materials offer a strategy to position molecular semiconductors within a highly defined, porous network. We developed thin films of a new semiconducting zinc phthalocyanine‐bridged PMO exhibiting a face‐centered orthorhombic pore structure with an average pore diameter of 11 nm. The exceptional degree of order achieved with this PMO enabled us to create thin films consisting of a single porous domain throughout their entire thickness, thus providing maximal accessibility for subsequent incorporation of a complementary phase. The phthalocyanine building blocks inside the pore walls were found to be well‐aggregated, enabling electronic conductivity and extending the light‐harvesting capabilities to the near IR region. Ordered 3D heterojunctions capable of promoting photo‐induced charge transfer were constructed by impregnation of the PMO with a fullerene derivative. When integrated into a photovoltaic device, the infiltrated PMO is capable of producing a high open‐circuit voltage and a considerable photocurrent, which represents a significant step towards potential applications of PMOs in optoelectronics.     

基于光栅投影和点云体积计算的过度包装检测系统

为了实现商品过度包装的无接触检测,设计了一种基于光栅投影的商品过度包装检测系统。首先利用投影仪和两个高分辨率摄像头,实现物体三维点云的获取,再提出物体点云的包围盒获取算法,计算物体的包围盒体积及三维点云体积,最后根据容积率和空隙率,检测商品包装是否过度。实验结果表明,系统能有效基于点云形状生成包围盒,点云体积计算准确度能达到95％,耗时比广泛使用的Poisson方法明显减少。     

Syntheses and characterizations of thermally degradable epoxy resins. III

In flip‐chip technology, the development of reworkable underfill materials has been one of the keys to the recovery of highly integrated and expensive board assembly designs through the replacement of defective chips. This article reports the syntheses, formulations, and characterizations of two new diepoxides, one containing secondary ester linkages and the other containing tertiary ester linkages, that are thermally degradable below 300 °C. The secondary and tertiary ester diepoxides were synthesized in three and two steps, respectively. Both compounds were characterized with NMR and Fourier transform infrared spectroscopy and formulated into underfill materials with an anhydride as the hardener and an imidazole as the catalyst. A dual‐epoxy system was also formulated containing the tertiary ester diepoxide and a conventional aliphatic diepoxide, 3,4‐epoxy cyclohexyl methyl‐3,4‐epoxycyclohexyl carboxylate (ERL‐4221E), with the same hardener and catalyst. The curing kinetics of the formulas were studied with differential scanning calorimetry (DSC). Thermal properties of cured samples were characterized with DSC, thermogravimetric analysis, and thermomechanical analysis. The dual‐epoxy system showed a viscosity of 18.7 and 0.87 P at 25 and 100 °C, respectively. The cured secondary, tertiary, and dual‐epoxy formulas showed decomposition temperatures around 265, 190, and 220 °C, glass‐transition temperatures around 120–140, 110–157, and 140–157 °C, and coefficients of thermal expansion of 70, 72, and 64 ppm/°C below their glass‐transition temperatures, respectively. The shear strength of the cured dual‐epoxy system decreased quickly with aging at 230 °C. The reworkability test showed that the removal of a chip underfilled with this material from the board was quite easy, and the residue on the board could be thoroughly removed with a mechanical brush without obvious damage to the solder mask. In summary, the synthesized tertiary epoxide can be used as a reworkable underfill for flip‐chip applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1796–1807, 2002     

《电工理论与电子技术》课程教学改革探讨

《电工理论与电子技术》是非电专业的一门技术基础课程，在非电类专业的教学计划中占有十分重要的地位。只有提高课堂教学效果、更新教学手段、加强实践教学环节，培养学生实践动手能力和创新精神，才能满足社会对电子电工技术人才的需求。