用于微全分析系统的数字化微流控芯片的研究

研制出一种基于介质上电润湿(electrowetting-on-d ielectric,EWOD)机制的可编程数字化微流控芯片。它采用“三明治”结构:受控离散液滴被夹在两极板之间;下极板以硅为衬底,掺杂多晶硅作为芯片微电极阵列,其上涂覆有Teflon(AF1600薄膜的S iO2作为疏水性介质层;上极板是涂覆有Teflon(AF1600疏水薄膜的透明电极。通过分析数字化微流控系统的基本操作(离散液滴的传输、拆分及混合)的物理机理和模拟优化,在35 V低驱动电压下实现了约0.35μL和0.45μL去离子水离散液滴的传输和合并,并在70 V驱动电压下实现了0.8μL液滴的拆分等操作。     

Demonstration of Four Fundamental Operations of Liquid Droplets for Digital Microfluidic Systems Based on an Electrowetting-on-Dielectric Actuator

An electrowetting-on-dielectric actuator is developed, in which the liquid is sandwiched between top and bottom plates. For the bottom plate, silicon wafer is used as the substrate, the heavily phosphorus-doped polysilicon film is deposited by low pressure chemical vapour deposition as the microelectrode array, and thermally grown SiO2 film as the dielectric layer. The top p/ate is a glass plate covered with transparent and conductive indium tin oxide as the ground electrode. In addition, a Teflon AF1600 film is spun on the surface of both the plates as the hydrophobic layer. The experimental results show that when the gap height between two plates is 133μm, a prototype of the device is capable of creating, transporting, merging and dividing droplets of deionized water in an air environment with a 70V at lOHz voltage pulse. This is also established by simulations using the computational fluidic software of CFD-ACE＋.     

基于介质上电润湿的微流体变焦透镜的研究进展

近年来,微流体变焦透镜的研究已展示出其在光学系统中的应用前景,其中基于介质上电润湿(Electrowet-ting on dielectric,EWOD)的微流体变焦透镜只需改变外加电压便能快速调节透镜焦距,并且具有尺寸小、结构灵活、功耗低、焦距调节范围广等许多突出优点而日益受到注目。在介绍EWOD机理的基础上,综述了目前基于EWOD的微流体变焦透镜的研究进展。     

基于微电子机械系统技术的高灵敏度电容式微传声器的研制

基于微电子机械系统（ＭＥＭＳ）技术的微传声器是当前国际上研究的热点。使用 ＭＥＭＳＩ艺制备的薄膜一般有着不可忽视的残余应力,极大的降低了膜的机械灵敏度。理论分析和数值模拟表明,纹膜结构可在不改变工艺条件的前提下,显著的降低残余应力的不良影响,大幅度增加膜的灵敏度。本文提出了一种使用ＭＥＭＳ技术制作的纹膜结构电容式微传声器,其制作工艺简单、重复性好,所用材料也能与 ＩＣＩ艺很好的兼容。圆片级测试的结果表明,在 １０ Ｖ的偏置电压下,这种微传声器在 ７ ｋＨｚ以下具有平直的频响,开路灵敏度可达 ４０ ｍv／Ｐａ,而其占用的芯片面积仅为 １．５ ×ｌ．５ ｍｍ２。进一步的研究可望将信号处理电路集成于片内,形成完整的微声学系统。     

Fabrication Process of Sol-Gel Spin Coating for SrBi2Ta2O9 Films Applied to FeRAM

We investigate SrBi2 Ta2 O9 （SBT） films prepared by the sol-gel spin method with different spin rates or different anneal conditions for the first layer of SBT, as promising ferroelectric layer materials applied to ferroelectric random access memory （FeRAM）. All the specimens in this experiment have similar SBT crystal orientations of （115）, （020）, （220）, and （135）. The Pt/SBT/Pt capacitor with coating of 3000rpm spin rate has a perfect rectangle shape of hysteresis loops, remanent polarization of 7.571μC/cm^2 and coercive voltage of 0.816 V at 5 V voltage amplitude. These characteristics are better than those with coating of 3500rpm spin rate, which is attributed to the influence for thickness and grain size of the film from depressed spin rate. Slow-rate anneal in the furnace for the first layer of SBT can improve the crystallization processes and properties for SBT layers slightly, compared with rapid thermal annealing. The ion damage from etching for the top electrode can influence leakage current characteristics of the Pt/SBT/Pt capacitor at positive voltage bias.     

微流控光学器件与系统的研究进展

微流控技术作为微全分析系统的关键与核心,一直是MEMS领域中的一个研究重点。随着微流控技术水平的不断提高以及与其它学科的不断渗透与融合,近年来已经涌现出一批令人注目的研究热点,其中微流控光学器件就是其典型代表。微流控技术与光学器件的融合,为传统光学器件的微型化、阵列化、低成本化以及高精度控制提供了可能。叙述了一些基于微流控技术的可变焦光透镜、显示器件、光开关、以及可调光纤光栅等新型光学器件的近期研究成果和应用背景。     

激光加热效应在硅显微Raman光谱测量中的影响

本文从理论和实验两方面研究了显微Raman光谱测量中,激光功率对单晶硅样品测量的影响。由于显微Raman光谱仪对激光的聚焦作用,使得激光对不同厚度的样品具有微区加热作用,被测样品产生不同程度的温升,从而对显微Raman光谱仪在硅材料应力和温度的测量中产生影响。实验结果证明,对无限厚硅样品,20mW的激光使Raman频移达到0.15cm-1;而对2μm厚的热薄硅样品,26mW的激光使Raman频移达到4.47cm-1。     

Preparation and Characteristics of Nanoscale Diamond-Like Carbon Films for Resistive Memory Applications

We propose diamond-like carbon （DLC） as the resistance change material for nonvolatile memory applications. Nanosecale DLC films are prepared by filtered cathodic vacuum arc technique and integrated to W//DLC/W structure devices. The deposited DLC film has a thickness of about 20nm and high spa fraction content. Reversible bistable resistive switching from a high resistance state to a low resistance state, and vice versa, is observed under appropriate unipolar stimulation pulses. High resistance switching ratio （larger than a thousand times） and low level of switching power （about 11 μW） are demonstrated. We propose that the mechanism of the repetitive resistive switching is the growth and breakage of conductive sp2-like filaments in the predominantly sp3-type insulating carbon upon applications of voltage pulses, which is consistent with the experimental results.     

Blue-Green Light Emission from a-SiCx：H-Based Fabry-Perot Microcavities

A Si-based novel Fabry-Perot microcavity device that can emit blue-green light at room temperature is proposed and fabricated, One of its Bragg reflectors consists of periodically stacked a-SiO2/a-Si：H layers deposited on the glass by plasma enhanced chemical vapour deposition, The other reflector is a sputtered Al film, The active region between both the reflectors is constructed by a p-type a-SiCx：H/intrinsic-type a-SiCx ：H junction fromwhich the electroluminescence （EL） is originated. The EL spectra of this device are recorded by RENISHAW RM2000, a sharp and strong EL peak at 483nm with FWHM of 20nm is observed when the device is driven by dc voltages of 8 V, 12 V and 18 V at room temperature. The intensity of EL increases with the applied voltage while the luminescence wavelength keeps unchanged. Compared with the EL spectra from the sample without the Bragg reflector, the luminescence intensity is about 10 times enhanced and the peak is narrowed greatly. The luminescence mechanism is analysed in detail.     

Comparison of Properties of Pt/PZT/Pt and Ru/PZT/Pt Ferroelectric Capacitors

Pb（Zr0.4Ti0.6）O3 film prepared by sol-gel spin coating on a Pt/Ti/SiO2/Si substrate is applied to ferroelectric capacitors with Pt or Ru as the top electrode. For the Pt/PZT/Pt and Ru/PZT/Pt ferroelectric capacitors, although with the same ferroelectric film, different top electrode materials incur different properties of PZT capacitors, such as fatigue, leakage, remanent and saturated polarization, except the similar crystal orientations of the PZT film. After 10^10 switch cycles, the remanent polarizations of the Ru/PZT/Pt and Pt/PZT/Pt capacitors decrease to 70% and 84%, respectively. The leakage current density of the latter increases obviously at positive bias after 108 switch cycles, compared with the former. Different materials for the top electrode bring different conditions at the PZT/top electrode interface. The influence of oxygen-vacancy concentration at the PZT/electrode interface and the influence of oxides of the electrode material at the PZT/electrode interface to charge injection can explain the difference of properties of the PZT capacitors with Pt or Ru as the top electrodes.