Recent advances in transistor performance of polythiophenes

Polythiophenes have long played a major role in the field of conducting polymers due to their relative ease of synthesis, good thermal and oxidative stability, high charge carrier mobility and ease of processing and they have found widespread use in electronic applications such as field-effect transistors (FETs), organic photovoltaics (OPVs), light-emitting diodes (LEDs) and electrochromic displays (ECDs). In this review, we summarize the most important synthetic approaches to thiophene-, thienothiophene- and other fused thiophene-based polymers, highlight a number of significant findings relating to their properties with an emphasis on device performance in organic field-effect transistors and reflect on existing challenges and future opportunities in the field.     

Enhanced performance of graphene transistor with ion-gel top gate

High-efficiency dielectrics are promising materials that may enable nanoelectronic devices, such as carbon nanotubes and graphene transistors, to reach their performance limits. A high current on/off ratio, low voltage operation, high on-current and current saturation were all realized in a chemical vapor deposition graphene transistor by using a high-efficiency ion-gel dielectric. Using a drift–diffusion device model based on the surface potential in the channel that also considers the contact resistance at the channel boundary, the output characteristics of the graphene transistor are simulated, which agrees well with the experimental data and indicates that the current saturation in the graphene channel is intrinsic ambipolar performance under low field conditions. We also demonstrate an ambipolar invertor based on these high performance graphene transistors with gain values as high as 4.     

Device and circuit-level performance of carbon nanotube field-effect transistor with benchmarking against a nano-MOSFET

ABSTRACT: The performance of a semiconducting carbon nanotube (CNT) is assessed and tabulated for parameters against those of a metal-oxide-semiconductor field-effect transistor (MOSFET). Both CNT and MOSFET models considered agree well with the trends in the available experimental data. The results obtained show that nanotubes can significantly reduce the drain-induced barrier lowering effect and subthreshold swing in silicon channel replacement while sustaining smaller channel area at higher current density. Performance metrics of both devices such as current drive strength, current on-off ratio (Ion/Ioff), energy-delay product, and power-delay product for logic gates, namely NAND and NOR, are presented. Design rules used for carbon nanotube field-effect transistors (CNTFETs) are compatible with the 45-nm MOSFET technology. The parasitics associated with interconnects are also incorporated in the model. Interconnects can affect the propagation delay in a CNTFET. Smaller length interconnects result in higher cutoff frequency.     

Diamond Electrodes

With their unique chemical stability and high electron mobility, boron-doped thin diamond films are likely to have favorable properties for a number of electrochemical applications. A review of the recent developments in this field is presented with critical evaluation of the experimental data. In particular, the relationship between the material's characteristics and the electrochemical behavior of the electrodes is discussed in detail. A number of potential applications for these electrodes are presented: for dimensionally stable electrodes in highly corrosive environments, for discharging toxic effluents, and for electrochemical sensors.     

Diamond polishing

The empirical know-how of single crystalline diamond polishing has been developed over centuries in the diamond gem cutting industry. Since the 1950s new and varied uses and potential applications for synthetically produced diamond have been consistently proposed and developed. This innovation process continues with the availability of ever better, more specialized and less costly single crystalline and polycrystalline diamond materials. Yet, the potential exploitation of this hardest of materials is still in its infancy. Polishing is a critical and limiting step for advancing diamond applications in terms of cost effective processing and the achievable material surface finish. The current state-of-the-art of polishing single crystalline and polycrystalline diamond materials is reviewed based on the published literature. The material removal process during traditional mechanical polishing using diamond grit and polishing wheels is strongly anisotropic and depends upon crystal planes and polishing directions. Wear debris analyses and molecular dynamic simulations led to the understanding that this anisotropy is primarily caused by a mechanically induced transition from diamond to an amorphous carbon phase rather than by microchipping as previously thought. Mechanical polishing also leads to subsurface damage and limits the achievable surface finish for single crystalline diamond. Advanced techniques are discussed to improve the polished crystal's surface quality. Mechanical polishing of polycrystalline diamond films and freestanding plates is particularly slow due to the intrinsic structure variations in such materials. To overcome these limitations faster polishing techniques have been developed and are reviewed and compared. These techniques introduce additional chemical and physical means of material removal extending the capabilities of mechanical polishing. There is no single method that can address all requirements, but the available variety affords the careful selection of an optimal process for a given task. Finally, while diamond polishing is a subject of interest since centuries, it still remains a very important research area required to unfold the promise of diamond as a technical material.     

金钢石的人工赋色

金刚石的人工赋一种颇发展前途的新工艺，是改善和提高金刚石使用价值的有效途径之一，本文阐述了金刚石人工赋色的原理、工艺及其效果，介绍了实施工艺示例。     

Effect of betaine supplementation on power performance and fatigue

Background  

The purpose of this study was to examine the efficacy of 15 days of betaine supplementation on muscle endurance, power performance and rate of fatigue in active college-aged men.     

Enhanced performance of hybrid power source under low temperature

The performance of a battery–electrical double layer capacitor (EDLC) hybrid power source at low ambient temperature has been experimentally analyzed. EDLC can enhance the performance of lead-acid battery as it acts as a buffer during charging and discharging, and plays more significant role at low temperature than room temperature. The behaviors of current and voltage of both battery and EDLC have been detailed studied, and described by a mathematical model. With EDLC assistance, the battery can maintain longer discharge duration at −25 and −10 °C, compared with the battery alone. Adding an EDLC in parallel with the battery exhibits a considerable capacity increase compared to battery standalone in continuous discharge processes: from 13.6 to 36.5 %, corresponding to 25 to 200 A. These improvements of capacity become even more significant at low temperature. The increases in available capacity of different pulse duty, amounted to 72, 58, and 4 % at 0.1, 0.5, and 0.9 duty cycle values, compared to the capacity measured at constant current rate, respectively (calculated by 50 A discharge).     

埋砂法复合电镀金刚石磨轮

在镀镍溶液中利用镍离子电沉积将经过特殊处理的金刚石镶嵌到基体表面,经过低应力高整平的镀镍液快速电镀,使镀层包覆到金刚石粒度的65％ ～ 70％高度的厚度出槽.改撒砂法为埋砂法加工,克服了高铁轨道板磨轮镀后动平衡严重破坏的弊端,提高了使用性能.     

人造金刚石散热材料

文章讨论了人造金刚石散热材料问题,包括金刚石的导热率、用人造金刚石制造散热材料的可行性以及研究这个问题可能的正确方法.     

Homoepitaxial Diamond Devices

Diamond has been proposed as an excellent material for high-temperature, high-power, and high-frequency applications. The interest in diamond electronics is due to its large electric breakdown field, high-saturated current velocity and high-thermal conductivity. As silicon and gallium arsenide devices begin to reach their performance limits, there is a need to develop new, better performing materials such as diamond. Significant progress in the development of diamond as a semiconducting material has been made and diamond has been implemented into numerous conventional and novel device designs. In this work homoepitaxial diamond material properties and device performance are reviewed. In summary, the large activation energy of boron-doped p-type diamond and phosphorus-doped n-type diamond severely limits diamond's use in conventional semiconductor device designs. The large activation energy reduces the number of charge carriers, which limits the current handling capability and produces temperature-dependent device performance. To overcome diamond's limitations, novel devices, such as enhancement mode field effect transistors (FETs) that use a hydrogenated surface conducting layer or pulsed doped devices with almost complete ionization, have been investigated. These devices require further development. The initial results show promise for high-temperature, high-frequency, and high-power applications.     

Diamond merged diode

To obtain high blocking voltages and low forward losses in power diode structures, a Schottky contact can be merged with a MIS contact or a pn-junction. In this configuration, the Schottky contact is responsible for a low forward threshold voltage and the MIS or pn-junction for a low reverse leakage current and a high breakdown voltage. In this study, a diamond merged diode structure has been fabricated and evaluated, containing simultaneously an Al or W:Si-Schottky contact and a boron/nitrogen pn-junction. The IV characteristics show a low forward barrier of 1.5 eV, a current rectification ratio of 10⁹ at R.T., and a reverse breakdown at 2.5 MV/cm. Rectification has been obtained up to 1000 °C (in vacuum).     

燃煤电厂湿烟气的除湿特性

燃煤电厂湿法脱硫后排放的烟气中含有大量水蒸气,造成大量水资源的浪费,溶液除湿工艺是水分回收技术之一。通过绝热型管式降膜除湿试验台,采用价格低廉的CaCl₂溶液为除湿剂,探究了湿烟气状态下溶液浓度、溶液温度、传质面积及进口温度对除湿性能的影响,试验得到了CaCl₂溶液除湿过程的传质系数,溶液除湿效率远高于清水冷凝除湿,为烟气除湿工艺的选择和性能预测提供了参考。     

可生物降解的(2-羟基-3-十二烷氧基)丙基-羟丙基壳聚糖的制备及其泡沫性和乳化性的研究

在相同实验条件下 ,先后将羟丙基和 (2 羟基 3 十二烷氧基 )丙基分别引入 3种不同相对分子质量的壳聚糖分子结构中 ,制得一系列可生物降解的两亲性的壳聚糖表面活性剂——— (2 羟基 3 十二烷氧基 )丙基 羟丙基壳聚糖 (HDP HPCHS)。通过红外光谱对其进行了结构表征 ,并在 0 2～ 1 0 0g/L质量浓度范围内测定了其泡沫性能和乳化性能。结果表明 :室温下 ,不同相对分子质量的HDP HPCHS均具有良好的泡沫性和乳化性 ,并且均随其相对分子质量的改变而呈现规律性变化。具体表现为 :HDP HPCHS的相对分子质量越高 ,达到最大起泡能力所需的溶液浓度越小 ,其乳化能力也越强 ;但其最大起泡能力和乳化层的稳定性却随相对分子质量的增大而下降。     

Gas evolution and power performance in direct methanol fuel cells

The use of acrylic cells and a CCTV camera for visually investigating the carbon dioxide gas evolution process inside an operating direct methanol fuel cell environment is demonstrated. Also, the effect of operating parameters on the system gas management, using a series of tests with different gas diffusion layer supporting materials, flow bed designs, cell sizes and exhaust manifold configurations, is studied. Carbon dioxide gas management is an important issue obstructing progress in viable direct methanol fuel cell systems development. Gas evolution mechanisms and gas management techniques are discussed and analysed with reference to several video picture and performance data. The data demonstrate that Toray carbon paper is not a suitable material for DMFCs due to its poor gas removal properties. A type carbon cloth shows relatively good gas removal behaviour. Increasing the liquid phase inlet flow rate is beneficial for gas removal. Increasing the current density results in higher gas production and in the formation of gas slugs, especially at low flow rates, which can lead to blocking of the channels and hence deterioration in the cell performance. A new flow bed design, based on a heat exchanger concept, is affective for gas management and gives a more uniform flow distribution in the flow bed channels. Using the results of this study, and the modelling techniques developed by our group, will are able to determine suitable operating conditions for our prototype 0.5kW cell DMFC stack.     

Fiber-Reinforced Diamond Matrix Composites

The feasibility of fiber-reinforced diamond matrix composites was examined. For this purpose, monofilament composite specimens were fabricated using SiC fibers. The diamond was deposited onto the fibers using plasmae-enhanced chemical vapor deposition. The mechanical properties of the composite were characterized using uniaxial tensile tests. The specimens exhibited multiple matrix cracking, followed by fiber fracture and fiber pullout. The measurements were used to obtain an estimate of the interface sliding stress and the in-situ fiber strength.