蛋类膜-壳结构启发制备兼具高灵敏度和宽检测范围的应变传感

为了解决可拉伸应变传感器的灵敏度与检测范围(最大和最小可拉伸性)之间相互制约的问题.受蛋类膜-壳结构的启发,本文提出了一种构筑具有高灵敏度、宽可拉伸应变传感器的新策略,即基于柔性可拉伸的表面接枝聚吡咯膜(s-PPy)(类似于蛋膜)和脆性金膜(类似于蛋壳)制备器件.Au和s-PPy膜在电学和机械性能上产生相互协同作用.A...     

D.C. conductivity versus temperature of a metallic complex of (CH)x with potassium

We have measured the electrical conductivity σ of heavily K-doped cis-(CH)_x as a function of temperature between 300 K and 4.2 K. A semiconductor-like behaviour of σ is observed and the attempt to explain our data led us to examine a conduction model involving tunnelling between potential barriers. Two activation energies are observed and the transition that occurs in the conductivity behaviour could arise from inhomogeneous doping.     

Effects of low level boron doping of the i-layer on the performance of SiC p-i-n devices

a-Si: H devices have been prepared by plasma decomposition of a silane mixture containing ppm levels of diborane. The level of background impurities was controlled by outgassing, monitored by residual gas analysis and finally measured in the solid by SIMS analysis. Two groups of samples were prepared which differed by an order of magnitude in their impurity concentration. The effect of boron addition to the i-layer differed strongly depending on the background impurity level. At high impurity levels ([O] = 1 × 10²⁰ atoms/cm³) a well defined maximum in device performance occurred at [B₂H₆] = 3 ppm, while at lower background levels boron addition served only to lower the device performance. Quantum efficiency measurements indicate that the changes in device performance are due to corresponding changes in the collection length and average μτ product. The ambipolar diffusion length determined by the surface photovoltage yielded similar results.     

一种无线宽带收发机I/Q失配校准和补偿技术

本文提出一种基于数字基带的无线宽带收发机中的发射链路I/Q失配的校准和补偿技术。数字基带发射用于I/Q失配校准的信号,经过RF收发机的发射链路、由平方功率检测器、带通滤波器组成的校准通路以及RF接收机的可变增益放大器,数字基带采集此信号并估计I/Q失配的大小,完成I/Q失配的校准和补偿,此技术相比于射频的自校准节省了面积和功耗。本技术已经成功用于IEEE802.11n,可以实现50dB以上的镜像抑制,完全满足了系统要求。     

基于蓝宝石纳米图形衬底上氮化镓生长的研究

利用两步生长法在蓝宝石纳米图形衬底（NPSS）上生长得到高质量的氮化镓薄膜。通过XRD和SEM对薄膜质量的表征和研究发现,为得到高质量的氮化镓（GaN）薄膜,在NPSS上生长时得到的最优缓冲层厚度为15nm,而在微米级尺寸的图形衬底（MPSS）上得到的最优缓冲层厚度远大于15nm。同时,在NPSS上生长氮化镓薄膜的过程中观察到一个有趣的现象,即GaN在NPSS上生长的初始阶段,氮化镓晶粒主要在图形之间的平面区域生长,极少量的GaN在衬底图形的侧面上聚集生长。这一有趣的现象明显不同于GaN在MPSS上的生长过程。接着,又在NPSS上生长了GaN基LED结构,并对其光电性能进行了研究。     

(PEDOT-PSS)-碳纳米管复合膜硅基太阳能电池

碳纳米管-Si(CNTs-Si)肖特基太阳能电池具有制作简单、成本低的优势。然而,受限于CNTs薄膜的电阻高、结区均匀性差、反光严重等因素,该类器件的光电转换效率仍较低。本文研究了聚3,4-乙撑二氧噻吩-聚苯乙烯磺酸盐(PEDOT-PSS)-CNTs复合透明膜的制备及其在硅太阳能电池中的应用。电流-电压曲线表明,PEDOT-PSS的引入可以大幅度提升CNTs-Si器件的光电转换效率(从5.9%到11.6%)。作为透明电极,复合膜中的取向CNTs可有效地收集和传导太阳能电池结区的光生空穴,而PEDOT-PSS则有效填补了CNTs膜的面内空隙,进而增加了肖特基结的面积。采用表面刻有倒金字塔结构的聚二甲基硅氧烷(PDMS)作为减反层,有效地降低入射光的反射,增加Si表面对光的吸收,进一步将(PEDOT-PSS)-CNTs-Si器件的光电转换效率提升至12.4%。电子束感生电流技术表明器件的光电转换主要基于复合膜与Si之间的肖特基结。     

Alcohol-assisted rapid growth of vertically aligned carbon nanotube arrays

Millimeter-to-centimeter scale vertically aligned carbon nanotube (VACNT) arrays are widely studied because of their immense potential in a range of applications. Catalyst control during chemical vapor deposition (CVD) is key to maintain the sustained growth of VACNT arrays. Herein, we achieved ultrafast growth of VACNT arrays using Fe/Al₂O₃ catalysts by ethanol-assisted two-zone CVD. One zone was set at temperatures above 850 °C to pyrolyze the carbon source and the other zone was set at 760 °C for VACNT deposition. By tuning synthesis parameters, up to 7 mm long VACNT arrays could be grown within 45 min, with a maximal growth rate of ∼280 μm/min. Our study indicates that the introduction of alcohol vapor and separation of growth zones from the carbon decomposition zone help reduce catalyst particle deactivation and accelerate the carbon source pyrolysis, leading to the promotion of VACNT array growth. We also observed that the catalyst film thickness did not significantly affect the CNT growth rate and microstructures under the conditions of our study. Additionally, the ultralong CNTs showed better processability with less structural deformation when exposed to solvent and polymer solutions. Our results demonstrate significant progress towards commercial production and application of VACNT arrays.     

Diamond based field-effect transistors with SiNx and ZrO2 double dielectric layers

A diamond-based field-effect transistor (FET) with SiN_x and ZrO₂ double dielectric layer has been demonstrated. The SiN_x and ZrO₂ gate dielectric are deposited by plasma-enhanced chemical vapor deposition (PECVD) and radio frequency (RF) sputter methods, respectively. SiN_x layer is found to have the ability to preserve the conduction channel at the surface of hydrogen-terminated diamond film. The leakage current density (J) of SiN_x/ZrO₂ diamond metal-insulator-semiconductor FET (MISFET) keeps lower than 3.88 × 10^− 5 A·cm^− 2 when the gate bias was changed from 2 V to − 8 V. The double dielectric layer FET operates in a p-type depletion mode, whose maximum drain-source current, threshold voltage, maximum transconductance, effective mobility and sheet hole density are determined to be − 28.5 mA·mm^− 1, 2.2 V, 4.53 mS·mm^− 1, 38.9 cm²·V^− 1·s^− 1, and 2.14 × 10¹³ cm^− 2, respectively.     

A bio-inspired multi degree of freedom actuator based on a novel cylindrical ionic polymer–metal composite material

In this work, we explore a promising electroactive polymer (EAP), called ionic polymer–metal composite (IPMC) as a material to use as a multi degree of freedom actuator. Configuration of our interest is a cylindrical IPMC with 2-DOF electromechanical actuation capability. The desired functionality was achieved by fabricating unique inter-digitated electrodes. First, a 3D finite element (FE) model was introduced as a design tool to validate if the concept of cylindrical actuators would work. The FE model is based upon the physical transport processes—field induced migration and diffusion of ions. Second, based upon the FE modeling we fabricated a prototype exhibiting desired electromechanical output. The prototype of cylindrical IPMC has a diameter of 1 mm and a 20 mm length. We have successfully demonstrated that the 2-DOF bending of the fabricated cylindrical IPMCs is feasible. Furthermore, the experimental results have given new insight into the physics that is behind the actuation phenomenon of IPMC.