太赫兹时域光谱法测定高电子迁移率晶体管的截止工作频率

随着高速半导体器件的发展,高电子迁移率晶体管(HEMT)的工作频率已经达到亚太赫兹波段,所以无法简单地通过传统电学方法进行检测。鉴于此,必须采用超快光学方法测定HEMT器件的截止工作频率。利用持续时间更短的飞秒脉冲激光瞬时关断处于饱和工作状态下的HEMT器件,并且采用太赫兹时域光谱技术测量在器件被关断后电流的变化情况(时间是皮秒量级),最后,利用所测量到的太赫兹波形(即源漏电流随时间变化的曲线)和截止工作频率的关系,直接推算出可达到亚太赫兹波段的HEMT器件的截止工作频率。     

石墨烯电极有机薄膜晶体管研究

利用化学气相沉积法生长的高性能的层状石墨烯,通过转移和图案化后用作电极,制备了底接触的并五苯有机薄膜晶体管(OTFTs)。原子力显微镜观察发现,石墨烯电极的厚度比一般的金电极薄的多,所以石墨烯电极厚度对并五苯晶粒的生长影响不大。电学性能研究得到器件的输出和转移曲线、开关电流比、阈值电压、场效应迁移率。转移曲线的关态电流约为10-9 A,电流的开关比超过103。基于底接触的并五苯OTFTs的最大场效应迁移率约2×10-2 cm2.V-1.s-1。     

有机薄膜晶体管阵列面向电子纸像素设计

讨论了有机薄膜晶体管(Organic Thin Film Transistor,OTFT)作为开关器件来驱动电子纸的像素设计,特别是像素电路结构、HSPICE模拟用模型参数和像素平面结构。讨论了有机薄膜晶体管制造过程,并用HSPIC模拟分析了有机薄膜晶体管结构和存贮电容大小对像素波形的影响,结果表明TFT结构的选择依赖于存贮电容的大小。     

A ring oscillator based on HIFETs

A hygroscopic insulator field-effect transistor (HIFET) ring oscillator with three inverters was built and tested under ambient laboratory conditions. An operating voltage of −2 V was used, yielding a peak-to-peak output voltage of 1.1 V and an oscillation frequency of 28 mHz. For Spice (simulation program with integrated circuit emphasis) simulation of the HIFET circuits the measured HIFET output characteristics were fitted to a DC (direct current) model and additional measurements were made to find the magnitude of the capacitive and resistive elements in the HIFET gate structure. The results indicated that HIFETs have a good potential for use in amplifier and sensor circuit applications where high operation speed is not crucial.     

Downscaling of n-channel organic field-effect transistors with inkjet-printed electrodes

In this contribution we demonstrate for the first time a downscaled n-channel organic field-effect transistors based on N,N′-dialkylsubstituted-(1,7&1,6)-dicyanoperylene-3,4:9,10-bis(dicarboximide) with inkjet printed electrodes. First we demonstrate that the use of a high boiling point solvent is critical to achieve extended crystalline domains in spin-coated thin films and thus high electron mobility >0.1 cm² V⁻¹ s⁻¹ in top-gate devices. Then inkjet-printing is employed to realize sub-micrometer scale channels by dewetting of silver nanoparticles off a first patterned gold contact. By employing a 50 nm crosslinked fluoropolymer gate dielectric, ∼200 nm long channel transistors can achieve good current saturation when operated <5 V with good bias stress stability.     

Lowering programmed voltage of organic memory transistors based on polymer gate electrets through heterojunction fabrication

The authors report on low operation voltage memory cells based on heterojunction ambipolar organic transistors with polymer gate electret (PGE). The introduction of the N,N′-dioctyl perylene diimide/pentacene heterojunction into the memory OFETs with PGE successfully lowered the memory cells’ reading, writing and erasing programmed voltages (reading voltage of 2 V, writing and erasing programmed voltages of 10 V). Meanwhile, the memory devices showed reproducible and durable memory behavior in more than 500 cycles’ testing. The built-in electric field-effect at heterojunction surface should efficiently reduce operation voltage of the memory devices.     

Plasma Polymerized Membranes for Isfet's

Abstract

A new type of membrane for ion sensitive field effect transistors (ISFET's) made by plasma polymerization has been proposed for electrode material. Tetrafluoroethylene, chlorobenzene, acetonitrile pure and doped with iodine served as monomers. Some structural features of the plasma polymer membranes are analyzed by ESCA- and IR- methods. Ion sensitivity and long term stability of the membrane are examined.     

Immunodetection of Herbicide 2,4-Dichlorophenoxyacetic Acid by Field-Effect Transistor-Based Biosensors

Abstract

An immunosensor method for determination of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was developed. It is based on the use of the competition between 2,4-D in analyzed probes and 2,4-D-peroxidase conjugate for binding with antibodies being immobilized on porous photo-activated cellulose membranes. These membranes were attached to the gate region of pH-sensitive field transistor (FET) and electrochemical detection of enzyme activity was carried out. Mixture of ascorbic acid (0.1 mM), o-phenylenediamine (1.0 mM), hydrogen peroxide (1.0 mM) was used as substrate solution. The initial rate of pH-shift of the FETs gate region was recorded as measured parameter.

The developed system permits to determine 2,4-D in water solutions for concentrations down to 1 ng/ml. This portable and inexpensive immunosensor meets modern requirements as analytical system for ecological monitoring.     

Characteristics of sputtered zinc-oxide films prepared by UBM sputtering for thin film transistors

In this work, we describe the characteristics of zinc-oxide (ZnO) thin films synthesized on Si (001) and Corning (7059) glass substrates by unbalanced magnetron (UBM) sputtering under various ZnO film thicknesses and RF powers. We investigated the characteristics of ZnO films' structural, optical, and electrical properties with various film thicknesses and RF powers for the active channel in a thin film transistor (TFT). We used the UBM sputtering system for high rate deposition of ZnO films. The ZnO film surface was rough and the grain size of the film increased with increasing RF power and film thickness. The electrical properties improved with the increase of RF power and film thickness. These results can be explained by the improvement of the crystallinity in the ZnO film related to the grain size increase with increasing RF power and ZnO film thickness.     

基于FPGA的dSPACE平台扩展方法

针对 dSPACE半实物仿真平台的 I/O端口、脉宽调制(PWM)路数不足的问题,提出了基于现场可编程门阵列(FPGA)的 dSPACE平台扩展方法。该方法通过建立 dSPACE和 FPGA之间的数据总线与指令总线,在 FPGA上构造指令表模块、I/O扩展模块、PWM发生器模块、A/D采样预处理模块和数据处理模块,并在MATLAB/Simulink中建立相应的控制模型,实现了dSPACE对FPGA扩展模块的控制和数据交换。实验结果表明,该方法能够节约 dSPACE资源,提高系统工作频率,增强 dSPACE的功能。