用于微测辐射热计的氧化钒薄膜的光电性能研究

采用磁控溅射方法在p-Si(100)衬底上制备了VO2和择优取向的V6O13混合相成分的薄膜.利用X射线衍射(XRD)分析、原子力显微镜(AFM)、傅立叶红外光谱(FT-IR)分析及四探针测试方法,研究了薄膜的相成分和红外吸收特性,并测试分析了薄膜的电学热稳定性.研究结果表明,通过这种方法制备的氧化钒薄膜具有较低的电阻率和较高的电阻温度系数(TCR),并且具有良好的热稳定性,可以作为微测辐射热计的热敏材料.     

反应离子束溅射沉积和还原退火工艺制备VO_x多晶薄膜

通过反应离子溅射沉积和后退火工艺制备出优质微测辐射热计用的氧化钒薄膜。对薄膜退火前后进行了扫描电子显微镜分析,结果表明,制备的VOx多晶薄膜致密均匀,退火后晶粒尺寸变大。电学测试表明,在室温时薄膜的方块电阻约为50kΩ,电阻温度系数为-0.022/K,满足制作高性能微测辐射热计的要求。     

氧化钒薄膜热敏特性的研究

为研究氧化钒薄膜在非致冷红外微测辐射热计中的应用,综述了制备工艺等诸多因素对氧化钒热敏特性的影响,对其机理进行了探究,结果表明掺杂和新的制备工艺是调整氧化钒热敏特性较为有效的方法.     

用于微测辐射热计的氧化钒薄膜制备

采用射频(RF)反应溅射法,在微结构衬底上制备氧化钒薄膜,研究了氧气压、衬底温度、退火条件及薄膜厚度对薄膜电阻及电阻温度系数(TCR)的影响.在氮气保护下,采用常规退火和快速升降温退火对薄膜进行热处理.结果表明:氧分压、退火条件和薄膜厚度对电阻温度系数影响较大,需综合考虑;衬底温度对薄膜电阻的影响较大,但对电阻温度系数的影响较小;与常规退火方法相比,采用快速升降温退火有利于薄膜电阻温度系数的提高;通过优化工艺参数,制得的薄膜电阻温度系数可达(-4%/℃)左右,满足微测辐射热计的要求.     

用于微测辐射热探测器的纳米VO2薄膜

用离子束溅射和后退火工艺制备了一种适用于微测辐射热探测器热敏材料的新型纳米结构二氧化钒(VO2)薄膜材料,薄膜具有平均粒度8 nm,在半导体相区具有电阻温度系数(TCR)为-7%/K,性能高于传统的VO2材料(平均粒度为1-2μm,在半导体相区具有TCR约为-2%/K).基于纳米结构的VO2薄膜材料的器件比基于传统的VO2薄膜材料具有更高的性能,而两者的噪声基本相当.     

二氧化钒微测辐射热计的制备及工艺

针对二氧化钒微测辐射热计在红外吸收型气体检测方面的应用,采用微电子机械系统(MEMS)体硅工艺制备了二氧化钒微测辐射热计,重点对关键工艺进行了研究;通过优化工艺参数及步骤,制得的微测辐射热计结构稳定,成品率高;对单元器件的性能参数进行测试,结果表明,在光源调制频率为1Hz时,单元器件的响应率为18.1kV/W;探测率为1.37×108cmHz1/2/W;热时间常数为72.4ms。     

氧化钒薄膜的结构、性能及制备技术的相关性

氧化钒薄膜及其在微电子和光电子领域中的已成为国际上新颖的功能材料研究的热点之一。本文综述了V2O5和VO2薄膜电学性能与薄膜组分的结构的相关性,比较了不同工艺制备的氧化钒薄膜的电学性能差异。     

V2O5熔体的微量氧化还原研究

将700、800、1100℃三种温度下的V2O5熔体制得V2O5溶胶,在非晶玻璃基片上将V2O5溶胶制成V2O5凝胶薄膜试样。通过对V205凝胶薄膜试样的电阻随温度的变化测试和电子能谱（ESCA）和X射线衍射分析发现V2O5凝胶薄膜中有四价钒的存在,本文从V2O5熔体的微量氧化还原和晶体结构的角度分析讨论了微量氧化还原影响钒离子价态变化的机理。     

氧化法热处理温度对氧化钒薄膜热敏特性的影响

采用直流磁控溅射法制备氧化钒薄膜,并采用不同的温度对其进行氧化法热处理,通过XRD、SEM、四探针薄膜电阻测试,分析了不同热处理温度对氧化钒薄膜的晶相特性与热敏特性的影响。实验分析证明热处理温度升高后(400℃)得到的薄膜热敏特性良好,其室温电阻为160KΩ·cm,室温电阻温度变化系数为-2.4%/℃,变温过程中(20~98℃)其平均值约-1.98%/℃,表明温度升高有利于改善薄膜热敏特性,在非制冷红外探测器应用方面具有发展潜力。     

多孔硅表面氧化钒热敏电阻薄膜的阻温特性

用电化学腐蚀法制备了具有不同导热系数的多孔硅样品(孔隙率为80％±2、厚度为110μm时,导热系数可降低至0．20 W／m·K),并在其表面沉积了氧化钒热敏薄膜,研究了多孔硅样品的热绝缘性能对氧化钒热敏薄膜阻温特性的影响．结果表明:多孔硅良好的热绝缘性使在其表面制备的氧化钒热敏薄膜电阻的灵敏度远高于在硅基底上制备的热敏电阻的(多孔硅和硅片上的氧化钒薄膜电阻随功率变化斜率分别为120 kΩ／μW和2．1 kΩ／μW),且热敏电阻的灵敏度随着多孔硅孔隙率和厚度的增大而升高．     

Optically transparent ZnO-based n-i-p ultraviolet photodetectors

An optically transparent tin-doped indium oxide/ZnO/NiO n-i-p heterostructure photodiode was fabricated by ion beam assisted e-beam evaporation. The diode clearly demonstrates rectifying current-voltage (J-V) characteristics with a current rectification ratio up to 10⁴ at bias ± 2 V and a low reverse current of ∼ 100 nA/cm² at − 5 V. Analysis of J-V characteristics including time dependence of the dark current shows that the leakage current at low biases is attributed to thermal generation via defect states, and at high biases, field-enhanced carrier generation from the ZnO layer dominates. Spectral response and linearity measurements indicate that such a diode is particularly suitable for low level of ultraviolet detection.     

Epitaxial growth and surface morphology of aluminum films deposited on mica studied by transmission electron microscopy and atomic force microscopy

The bulk structure and epitaxial growth of aluminum films deposited on mica substrates by thermal evaporation in a wide temperature range (16-550 °C) in high vacuum were investigated by transmission electron microscopy and transmission electron diffraction. The surface morphology of the films was observed and analyzed by atomic force microscopy. The films prepared at room temperature consist of single crystals having a diameter of 90 ± 40 nm with (111) planes. The surface of the films comprises spherical grains with morphology that is caused by self-shadowing during the deposition. The surface of the films becomes smoother as the temperature increases, and atomically-smooth surfaces with a root-mean-square roughness of about 0.45 nm over an area of 1 μm² are obtained at 250-350 °C. The crystals are oriented randomly along the [111] direction perpendicular to the substrate. The surface of the films consists of larger (> 300 nm) grains with terraces, and the surface becomes rough above 400 °C. Films with well-oriented single crystals along the [111] direction perpendicular to the substrate are obtained above 520 °C. The films grown epitaxially at 520-550 °C are characterized by the isolated grains with a diameter of 1220 ± 450 nm.     

technical note Linear variable differential transformers — Practical hints

Some years ago, a requirement existed for the development of a transducer of the LVDT type having the greatest possible sensitivity and of the smallest possible size. It was developed by a purely intuitive process and resulted in a series of devices having a variety of practical applications. In particular, its use as an extensometer could be of interest in the field of strain measurement.     

Enhancement of the efficiency and the color stabilization in green organic light-emitting devices with multiple heterostructures acting as a hole transport layer

The electrical and the optical properties of organic light-emitting devices (OLEDs), with and without multiple heterostructures consisting of N, N-bis-(1-naphthyl)-N, N-diphenyl-1,1-biphenyl-4,4-diamine (NPB)/5,6,11,12-tetraphenylnaphthacene (rubrene) acting as a hole transport layer (HTL), were investigated. The OLEDs with 3 periods of NPB/mixed rubrene:NPB multiple heterostructures acting as an HTL showed the highest luminances and efficiencies. While the electroluminescence (EL) peak corresponding to the rubrene layer did not appear for the OLEDs with 3 periods of NPB/mixed rubrene:NPB multiple heterostructures, only the EL peak related to the tris (8-hydroxyquinoline) aluminum layer was observed. The Commission Internationale de l’Eclairage chromaticity coordinates of the OLEDs with 3 periods of NPB/mixed rubrene:NPB multiple heterostructures at 14 V were (0.321, 0.531), indicative of a deep stabilized green color.     

Fabrication and characterization of NiO/ZnO/ITO p-i-n heterostructure

Transparent oxide semiconductors (TOSs) are promising materials for a variety of optoelectronic applications such as UV detectors. While several TOS-based p-n and p-i-n diodes have been recently reported, the high reverse dark current still poses a major issue. In this work, we report on a NiO/ZnO/ITO p-i-n heterostructure with reduced dark current level suitable for practical applications. Ion beam-assisted e-beam evaporation was used to deposit both p-type NiO and intrinsic ZnO layers, while a conventional sputtering system was used to prepare the ITO layer. Samples with sputtered ZnO layer were also fabricated for comparison. The diodes demonstrated clear rectifying I-V characteristics with a current rectification ratio up to 10⁴ at bias voltages of ± 1 V. The lowest level of reverse dark current (∼ 10 nA/cm² at − 5 V) is observed in samples with ZnO deposited by ion beam-assisted e-beam evaporation. In comparison, diodes with sputtered ZnO layer show two orders of magnitude higher dark current. Analysis of the quasi-static J-V characteristics, including time dependence behavior, shows that the dark current can be attributed to thermal generation of charge carriers via deep defects states in the ZnO layer and charge injection from the contacts. Electrical and optical properties of the TOS films are presented and discussed along with deposition conditions and device performance.     

聚醚醚酮的结晶与熔融行为研究

研究了PEEK在高于熔点的温度范围内处理时的结晶行为以及结晶后的熔融行为。发现处理时熔融的PEEK将同时发生交联与结晶,交联使未结晶的部分结晶受阻,结晶使尚存的晶片增厚,从而导致PEEK在DSC上出现对应于不同晶体结构的新的熔融双峰,并在此基础上提出了处理过程中PEEK结构变化的模型。此外,还发现处理后的PEEK的熔点,可高于目前已报导的平衡熔点。     

The spectrum of cosmic-ray electrons measured with H.E.S.S.

The measurement of very-high-energy cosmic-ray electrons is intrinsically difficult due to the very steep electron spectrum with low fluxes and an enormous background of hadronic cosmic rays. The large collection areas needed for such a measurement can be provided by ground-based imaging atmospheric Cherenkov telescopes. The High Energy Stereoscopic System (H.E.S.S.) has performed the first ground-based cosmic-ray electron measurement and thereby extended the measured range of the spectrum to several TeV. Here the H.E.S.S. measurement is presented, as well as an extension of the H.E.S.S. spectrum towards lower energies. At these energies, H.E.S.S. can probe recent ATIC measurements, which have been interpreted in terms of dark matter scenarios.     

尼龙—6与羧基化改性LDPE共混体系的结构研究

通过密度测定、Molau实验、二甲苯萃取抽出物的IR分析,测定了尼龙-6与各种改性聚乙烯的结构,发现尼龙-6分子末端的胺基与MAH-g-LDPE的酸酐及离聚体的羧酸发生化学反应,生成的接枝物起到了共混体系增容剂的作用,改善了体系的亲合性。DSC测定表明,各种LDPE的加入均会使共混物中尼龙的结晶速率加快,Avrami指数上升。     

Enhancement of the lifetime in organic light-emitting devices fabricated utilizing wide-bandgap-impurity-doped emitting layers

The degradation behaviors of the electrical and the optical properties of organic light-emitting devices (OLEDs) fabricated with an emitting layer (EML) doped with or without a wide-bandgap-impurity were investigated. The OLEDs with a wide-bandgap-doped Alq₃ EML were more stable than those with an undoped Alq₃ EML. The existence of the doped wide-bandgap-impurity in the EML decreased the trap-charge density in the EML, resulting in an increase in the number of electrons in the Alq₃ EML. That increases in the number of electron in the Alq₃ EML for the OLEDs with a wide-bandgap-impurity decreased the staying time of the holes in the Alq₃ EML, resulting in an enhanced lifetime for the OLEDs. These results indicate that OLEDs with a wide-bandgap-impurity-doped EML hold promise for potential applications in long-lifetime OLED displays.     

电流变材料设计与制备研究进展

简述了电流变液的转变机理发展现状,重点阐述了电流变材料的设计、制备及性能研究进展,并对影响电流变效应的有关材料因素作了深入探讨。