磁性纳米颗粒膜的微磁学模拟

用微磁学方法对磁性纳米颗粒膜的磁特性进行了模拟，采用的模型是由122个磁性纳米颗粒组成的面心立方(fcc)结构体系.结果表明：在该体系中，偶极相互作用对体系的静态磁结构的影响显著，而交换相互作用的影响表现不明显.在此基础上，本文还采用有效媒质理论计算分析了磁性合金颗粒不同体积比时颗粒膜的磁谱和表征电磁参量发生显著变化的逾渗现象和逾渗阈值.并完成了对高磁损耗磁性纳米颗粒膜的材料设计. 关键词： 微磁学 纳米颗粒膜 逾渗阈值 磁导率 材料设计     

FeCoB-SiO2磁性纳米颗粒膜的微波电磁特性

采用交替沉积磁控溅射工艺制备了超薄多层的FeCoB SiO2 磁性纳米颗粒膜 .利用x射线衍射仪、扫描探针显微镜、透射电子显微镜分析了薄膜的微结构和形貌特征 .采用振动样品磁强计、四探针法、微波矢量分析仪及谐振腔法测量薄膜试样的磁电性能和微波复磁导率 .重点对SiO2 介质相含量、薄膜微结构对电磁性能产生重要影响的机理做了分析和探讨 .结果表明 :这类FeCoB SiO2 磁性纳米颗粒膜具有良好的软磁性能和高频电磁性能 ,2GHz时的磁导率 μ′高于 70 ,可以应用于高频微磁器件或微波吸收材料的设计     

InGaZnO薄膜晶体管泄漏电流模型

研究了非晶氧化锌镓铟薄膜晶体管(amorphous InGaZnO thin-film transistor,InGaZnO TFT)的泄漏电流模型.基于Poole-Frenkel热发射效应和热离子场致发射效应的泄漏电流产生机制,分别得到了高电场和低电场条件下的载流子产生-复合率.在此基础上推导得到了InGaZnO TFT的分段式泄漏电流-电压数学模型,并利用平滑函数得到了关断区和亚阈区连续统一的泄漏电流模型.所提出的泄漏电流模型的计算值和TCAD模拟值与实验结果较为吻合.利用所提出的InGaZnO TFT泄漏电流模型和TCAD模拟,讨论了InGaZnO TFT不同的沟道宽度、沟道长度和栅介质层厚度对泄漏电流值的影响.研究结果对InGaZnO TFT集成传感电路的设计具有一定参考价值.     

Concise Modeling of Amorphous Dual-Gate In-Ga-Zn-O Thin-Film Transistors for Integrated Circuit Designs

An analytical model for current–voltage behavior of amorphous In-Ga-Zn-O thin-film transistors(a-IGZO TFTs)with dual-gate structures is developed.The unified expressions for synchronous and asynchronous operating modes are derived on the basis of channel charges,which are controlled by gate voltage.It is proven that the threshold voltage of asynchronous dual-gate IGZO TFTs is adjusted in proportion to the ratio of top insulating capacitance to the bottom insulating capacitance(C_(TI)/C_(BI)).Incorporating the proposed model with Verilog-A,a touch-sensing circuit using dual-gate structure is investigated by SPICE simulations.Comparison shows that the touch sensitivity is increased by the dual-gate IGZO TFT structure.     

铟镓锌氧薄膜晶体管的悬浮栅效应研究

为了避免光照对铟镓锌氧薄膜晶体管(InGaZnO thin film transistors,IGZO TFTs)电学特性的影响,IGZO TFT要增加遮光金属层.本文研究了遮光金属栅极悬浮时,IGZO TFT的输出特性.采用器件数值计算工具TCAD(technology computer-aided design)分析了IGZO层与栅介质层界面处电势分布,证实了悬浮栅(floating gate,FG)IGZO TFT输出曲线的不饱和现象是由悬浮栅与TFT漏端的电容耦合造成.基于等效电容的电压分配方法,提出了悬浮栅IGZO TFT电流的一阶模型.TCAD数值分析及一阶物理模型结果与测试具有较高程度的符合,较完整地解释了悬浮栅IGZO TFT的电学特性.     

Electro-statically controllable graphene local heater

We report on current-induced thermal power investigation of graphene nanostructure for potential local-heating applications. It is found that the efficiency of heating can be greatly improved if graphene is patterned into structures with narrow width and long channel. In a narrow graphene-ribbon, the Joule heating power exhibits an obvious dependence on the back-gate voltage. By monitoring Raman spectra, the temperature of graphene-ribbon can be determined. The temperature of graphene-ribbon is modulated by the electric field effect when the sample is sourced with a relatively high current.     

稀土元素对磁损耗型CoFeZrRE合金微波特性的作用

采用机械合金化工艺(MA)制备了在微波频段具有较高磁损耗的CoFeZrRE材料。在工艺条件对所合成材料性能影响的研究基础上，主要研究了材料组分中掺杂稀土元素对合成材料微波磁导率的影响。结果表明，稀土元素的掺入能有效调整材料的微波磁导率及其频响特性；加入适量的Tb，有利于获得高的微波磁导率和大的磁损耗。还用数值计算模拟方法得到了2～18GHz该材料的反射率曲线，结果表明该材料有可能应用于吸波材料的设计和制备中。     

同步对称双栅InGaZnO薄膜晶体管电势模型研究

研究了同步对称双栅氧化铟镓锌薄膜晶体管(InGaZnO thin film transistors,IGZO TFTs)的沟道电势,利用表面电势边界方程联合Lambert函数推导得到了器件沟道电势的解析模型.该模型考虑了IGZO薄膜中存在深能态及带尾态等缺陷态密度,能够同时精确地描述器件在亚阈区(sub-threshold)与开启区(above threshold)的电势分布.基于所提出的双栅IGZO TFT模型,讨论了不同厚度的栅介质层和有源层时,栅-源电压对双栅IGZO TFT的表面势以及中心势的调制效应.对比分析了该模型的计算值与数值模拟值,结果表明二者具有较高的符合程度.     

双层螺旋环超表面复合吸波体等效电路模型及微波损耗机制

针对超材料吸波频带窄的问题,采用金属螺旋环超表面与碳纤维吸波材料相复合的方式,设计了宽频高性能复合吸波体.研究发现,在碳纤维吸波材料中引入双层螺旋环超表面能显著增强吸收峰值和吸波带宽,且适当增加螺旋环初始线长和吸收层厚度有利于提高复合吸波体的吸波性能, 9.2—18.0 GHz频段的反射损耗均优于–10 dB (带宽达8.8 GHz),吸收峰值达–14.4 dB.利用S参数计算得到螺旋环-碳纤维复合吸波体的等效电磁参数和特征阻抗呈现多频点谐振特性,通过构建双层螺旋环超表面等效电路模型,定量计算了复合吸波体的电磁谐振频点,发现由等效电路模型获得的谐振频点计算值与仿真值基本相符,说明该复合吸波体多频点电磁谐振是宽频电磁损耗的主要机制.     

Surface potential-based analytical model for InGaZnO thin-film transistors with independent dual-gates

An analytical drain current model on the basis of the surface potential is proposed for indium-gallium zinc oxide(InGaZnO)thin-film transistors(TFTs)with an independent dual-gate(IDG)structure.For a unified expression of carriers’distribution for the sub-threshold region and the conduction region,the concept of equivalent flat-band voltage and the Lambert W function are introduced to solve the Poisson equation,and to derive the potential distribution of the active layer.In addition,the regional integration approach is used to develop a compact analytical current-voltage model.Although only two fitting parameters are required,a good agreement is obtained between the calculated results by the proposed model and the simulation results by TCAD.The proposed current-voltage model is then implemented by using Verilog-A for SPICE simulations of a dual-gate InGaZnO TFT integrated inverter circuit.