基于CNFET的低功耗三值门电路设计

通过对碳纳米场效应晶体管(Carbon Nanotube Field Effect Transistor,CNFET)的研究,提出一种基于CNFET的低功耗三值门电路设计方案.该方案在分析CNFET结构及其不同尺寸的碳纳米管对应于不同阈值电压特性的基础上,以多值逻辑理论为指导,设计基于CNFET的三值反相器、与非门、或非门等单元门电路,最后利用HSPICE对所设计的电路进行仿真.结果表明:所设计电路具有正确的逻辑功能,与传统三值门电路相比,三值CNFET门电路平均传输速度提高52.7%,平均能耗节省54.9%.     

第9届化学传感器国际会议

本届大会于2002年7月7日至10日在美国Boston市召开,由Elsevier科学公司主办。     

硅基底石墨烯器件的现状及发展趋势

石墨烯是一种由单层碳原子紧密排列而形成的具有蜂窝状结构的二维晶体材料,特殊的结构赋予了其优异的性能,如高载流子迁移率、电导率、热导率、力学强度以及量子反常霍尔效应.由于石墨烯优异的特性,迅速激起了人们对石墨烯研究以及应用的热情.石墨烯沉积或转移到硅片后,其器件构建与集成和传统硅基半导体工艺兼容.基于石墨烯的硅基器件与硅基器件的有机结合,可以大幅度提高半导体器件的综合性能.随着石墨烯制备工艺和转移技术的优化,硅基底石墨烯器件将呈现出潜在的、巨大的实际应用价值.随着器件尺寸的纳米化,器件的发热、能耗等问题成为硅基器件与集成发展面临的瓶颈问题,石墨烯的出现为解决这些问题提供了一种可能的解决方案.本文综述了石墨烯作为场效应晶体管研究的进展,为解决石墨烯带隙为零、影响器件开关比的问题,采用了量子限域法、化学掺杂法、外加电场调节法和引入应力法.在光电器件研究方面,石墨烯可以均匀吸收所有频率的光,其光电性能也受到了广泛的关注,如光电探测器、光电调制器、太阳能电池等.同时,石墨烯作为典型的二维材料,其优越的电学性能以及超高的比表面积,使其作为高灵敏度传感器的研究成为纳米科学研究的前沿和热点领域.     

高跨导氢终端多晶金刚石长沟道场效应晶体管特性研究

基于多晶金刚石制作了栅长为4 pm的铝栅氢终端金刚石场效应晶体管.器件的饱和漏源电流为160 mA/mm,导通电阻低达37.85Ω·mm,最大跨导达到32 mS/mm,且跨导高于最大值的90%的栅压(V_(GS))范围达到3 V(-2 V≤V_(GS)≤-5 V).通过传输线电阻分析以及器件的导通电阻和电容-电压特性分析,发现氢终端多晶金刚石栅下沟道中的空穴面浓度达到了1.56×10~(13)cm~(-2),有效迁移率在前述高跨导栅压范围保持在约170 cm~2/(V·s).分析认为,较低的栅源和栅漏串联电阻、沟道中高密度的载流子和在大范围栅压内的高水平迁移率是引起高而宽阔的跨导峰和低导通电阻的原因.     

Matrix method for the solution of RF field perturbations due to local frequency shifts

To tune the accelerating field to the design value in a periodical radio frequency accelerating structure, Slater＇s perturbation theorem is commonly used. This theorem solves a second-order differential equation to obtain the electrical field variation due to a local frequency shift. The solution becomes very difficult for a complex distribution of the local frequency shifts. Noticing the similarity between the field perturbation equation and the equation describing the transverse motion of a particle in a quadrupole channel, we propose in this paper a new method in which the transfer matrix method is applied to the field calculation instead of directly solving the differential equation. The advantage of the matrix method is illustrated in examples.     

保偏微纳光纤倏逝场传感器

近年来,保偏微纳光纤以其高双折射特性和强倏逝场效应引起了研究者的关注.本文从保偏微纳光纤的结构类型、制备方法和模式双折射特性等出发,介绍了目前不同类型保偏微纳光纤倏逝场传感器的构造特征与实现方法,利用保偏微纳光纤在两个垂直偏振方向的倏逝场对外界的不同响应,可制成偏振相关的干涉型或光栅型等传感器件.本文探究了包括超高折射率灵敏度特性和温度不敏感特性等的内在产生机理,并考察了保偏微纳光纤倏逝场传感器在折射率、湿度、磁场和特异性DNA分子探测等方面的应用,其结果对微纳光纤及其传感器的研究和应用具有重要的意义.     

The fabrication and characterization of 4H SiC power UMOSFETs

The fabrication of 4H-SiC vertical trench-gate metal-oxide-semiconductor field-effect transistors(UMOSFETs) is reported in this paper.The device has a 15-μm thick drift layer with 3×1015 cm-3 N-type doping concentration and a 3.1μm channel length.The measured on-state source-drain current density is 65.4 A/cm2 at Vg = 40 V and VDS = 15 V.The measured threshold voltage(Vth) is 5.5 V by linear extrapolation from the transfer characteristics.A specific on-resistance(Rsp-on) is 181 mΩ·cm2 at Vg = 40 V and a blocking voltage(BV) is 880 V(IDS = 100 μA@880V) at Vg = 0 V.     

A novel radio frequency coil for veterinary magnetic resonance imaging system

In this article,a novel designed radio frequency (RF) coil is designed and built for the imaging of puppies in a V-shape permanent magnetic resonance imaging (MRI) system.Two sets of Helmholtz coil pairs with a V-shape structure are used to improve the holding of an animal in the coil.The homogeneity and the sensitivity of the RF field in the coil are analysed by theoretical calculation.The size and the shape of the new coil are optimized and validated by simulation through using the finite element method (FEM).Good magnetic resonance (MR) images are achieved on a shepherd dog.     

蒽及其衍生物在有机场效应晶体管中的应用

近年来,有机场效应晶体管因其低成本、可低温制备、与柔性衬底兼容,以及能够大面积制备等优势而备受关注,其性能也在不断提高。其中并苯类化合物作为一类非常重要的有机半导体材料得到了广泛的关注和研究。渡越时间法测试表明蒽的迁移率能够达到3.0 cm²V^-1s^-1,应该具有较好的场效应晶体管应用。人们对蒽及其衍生物进行了一系列的研究,取得了很大的成功。这里,我们对蒽及其衍生物在有机场效应晶体管中的应用做一个较为全面的综述,期望为国内外同行提供一定的参考。     

Experimental study on SC RF cavities by using China large grain niobium for ILC

Large grain niobium has the potential of simplifying the production sequence and consequently reducing the cost of the superconducting RF cavities for ILC. To investigate the feasibility of fabrication and the possibility to achieve high gradient by large grain cavities, two 1.3GHz cavities were made of China large grain niobium and a series of vertical tests were carried out following several different surfaces treatment procedures. Two cavities have both reached the high gradient of more than 43MV/m repeatedly and the maximum accelerating field of 47.9MV/m has been achieved by China large grain niobium. This paper introduces the features of the fabrication and surface treatments on the large grain cavities and presents the preliminary results of the research.