水热因素对ZnO纳米材料气敏性能的影响

通过水热法合成了不同形貌的氧化锌(ZnO)气敏传感材料,利用X射线衍射仪和热场发射扫描电子显微镜对其进行了结构表征和分析,研究了不同的水热因素对其形貌的影响。利用Agilent B2900A quick I/V测试软件测试了其对乙醇气体的敏感性。实验结果表明:前驱体浓度、反应时间和反应温度会对ZnO纳米棒的生长造成显著影响。在前驱体浓度为20 mmol/L、反应时间为8 h、反应温度为95℃的条件下进行水热反应能得到较高质量和良好长径比的纳米线。通过气敏性能测试发现该条件下制备的样品在使用叉指电极时响应度为79%,响应时间和恢复时间均为4 s,表明该条件下制备出的气敏传感材料具有良好的响应度、响应时间和恢复时间。     

氧化钨纳米纤维的制备及其对H_2S的气敏特性北大核心

利用静电纺丝法制备了氧化钨(WO_3)纳米纤维。使用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对样品的物相结构和微观形貌进行表征。分析结果表明:制备的WO_3纳米纤维由众多纳米颗粒组装而成,且平均直径约为200 nm。同时,研究了基于WO_3纳米纤维的气体传感器对H_2S的气敏特性。实验结果表明:在工作温度为150℃时,该传感器对体积分数为2×10^(-5)的H_2S气体的响应达到72,响应时间和恢复时间分别为4 s和21 s,且检测极限为5×10^(-9),表明该传感器在低体积分数H_2S气体检测方面有实际应用价值。     

集成型二氧化锡纳米棒酒精传感器的自组装研制

为了有效提高酒精传感器的探测灵敏度,通过热蒸发SnO2和活性炭的混合粉末的自组装方式直接在Cd-Au梳状交叉电极上制备了一层SnO2纳米棒气敏层,从而构成了SnO2纳米棒气敏传感器,经测试,此传感器对于超低浓度范围（2×10^-6～10×10^-6）的酒精具有0．83～1．33的高探测灵敏度。继而从气敏机制、自组装制备方式、SnO2纳米棒的比表面特性及SnO2纳米棒的尺度（低于得拜长度）等角度解释此传感器对超低浓度酒精具有高气敏特性的原因。     

SnO2纳米棒的制备及其气敏特性研究

利用室温固相反应方法,合成了SnO2纳米颗粒前驱物。在NaCl+KCl熔盐介质中,于660℃下焙烧前驱物,合成了SnO2纳米棒。利用TEM、XRD和XPS对SnO2纳米棒形貌、成分进行了表征和分析。结果表明,SnO2纳米棒直径为20~30nm,长度从几百纳米到几微米。以SnO2纳米棒为原料,制备了厚膜气敏元件,在工作温度为300℃左右时,元件对乙醇具有较高的灵敏度、好的选择性和响应恢复特性。     

白钨矿结构BiVO4的水热合成及其可见光催化性能

以Bi(NO3)3·5H2O和NH4VO3为原材料,采用水热法合成了BiVO4可见光催化材料,并采用XRD、SEM和UV-Vis等对合成产物的物相结构、形貌、光吸收性能以及光催化性能进行了研究。研究表明,反应体系的pH值对合成产物的物相结构具有重要的影响,在酸性和弱碱性条件下可获得具有不规则纳米片状形貌的单斜白钨矿结构BiVO4晶体。合成产物对波长小于525nm的光具有强烈的吸收。水热条件的不同直接影响着产物对甲基橙溶液的可见光催化降解性能,在Bi∶V比例为1∶1,同时pH值为3.08并于160℃下水热处理1h所合成的BiVO4晶体对甲基橙溶液具有最佳的可见光催化活性。     

氧化铜纳米棒的水热合成及其气敏性能研究

以Cu(NO3)2·3H2O为铜源,氢氧化钠为pH调节剂,CTAB为表面活性剂,在150℃下水热反应24h成功制备出氧化铜纳米棒。通过TEM,XRD对其进行了表征。结果表明:所制得的材料为具有单斜晶系的氧化铜纳米棒,其长度为300～500nm,直径为40～50nm。通过静态配气法,对其在不同工作温度下的气敏性能进行了研究。发现:采用p型氧化铜纳米棒所制得的元件在250℃下,对体积分数为50×10–6的氯气有较好的气敏性能,灵敏度为4.5,响应/恢复时间为8s/40s。     

ZnO微球的自组装及其发光性能研究

采用水热法合成了不同形貌的ZnO微球,利用XRD、TG-DSC、FT-IR、PL和SEM等分析了水热产物及其焙烧产物的形貌、结构和光致发光性能.结果表明,水热温度及焙烧过程对产物有显著影响,随着水热温度的升高,水热产物的形貌逐步由牡丹花状向鹅卵石状转变,经600℃焙烧1h后得到形貌各异、直径10～20 μm的ZnO微球,其中水热温度较低的ZnO微球为细纳米片组成的海胆状,水热温度较高的为ZnO纳米棒组装成的鹅卵石状.PL分析表明不同形貌的ZnO微球均具有绿光发射特性.     

NiO纳米棒的制备及其室温下NO_x气敏性研究

在碱性条件下,以六水合氯化镍为基底,以尿素为沉淀剂,温度为180℃时,采用水热法制备了氢氧化镍中间体,将其进行焙烧得到氧化镍粉体。利用X射线衍射(XRD)和扫描电镜(SEM)对样品的组成和形貌进行分析,本实验所制备的氧化镍呈一维棒状结构,纳米棒直径为100～400 nm,长度从几百个纳米到十几个微米。将Ni O材料组装成气敏元件,在室温下对NO_x进行气敏测试,结果表明,该材料在室温下对体积分数为9.7×10~(–5)的NO_x有良好的气敏响应,响应可达到1.20,响应时间为14.0 s,且有良好的选择性。     

集成型三氧化锡纳米棒酒精传感器的自组装研制

为了有效提高酒精传感器的探测灵敏度,通过热蒸发SnO2和活性炭的混合粉末的自组装方式直接在Cd-Au梳状交叉电极上制备了一层SnO2纳米棒气敏层,从而构成了SnO2纳米棒气敏传感器,经测试,此传感器对于超低浓度范围(2×10-6～10×10-6)的酒精具有0.83～1.33的高探测灵敏度.继而从气敏机制、自组装制备方式、SnO2纳米棒的比表面特性及SnO2纳米棒的尺度(低于得拜长度)等角度解释此传感器对超低浓度酒精具有高气敏特性的原因.     

ZnSnO_3气敏材料的溶解-热解法制备及其性能

以Sn粉、Zn粉为原料,采用溶解-热解法,在草酸体系中,制备了Sn-Zn复合氧化物。通过TGA-DTA、XRD和SEM等手段,对产物的物相、形貌进行表征,并研究其气敏性能。结果表明:经700℃煅烧制得的钙钛矿结构ZnSnO3材料所制气敏元件,在工作温度为175℃时,对体积分数为50×10-6H2S及乙醇气体有较高的灵敏度,分别为53.00,47.00;工作温度为225℃时,对体积分数为50×10-6乙醇有较好的选择性。     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.