Nondestructive imaging of grain boundaries in polycrystalline materials using evanescent microwave probes

Nondestructively imaging electrical properties of materials with very high spatial resolution is of great importance in analyzing electronic, semiconductor, superconductor, biological, and other materials. In this work, we introduce and discuss a new family of probes that use evanescent microwave fields to image microwave properties of materials. We discuss and explain new equipment and programming methods that have been incorporated into our setup to improve its resolution and imaging capabilities. In addition, new scanning techniques are discussed that allow for the affluence region of microwave probe to be characterized. Finally, images that were obtained from ceramics, diamond, and other types of materials are discussed to demonstrate the improved imaging capability of the evanescent microwave probe in detecting grain boundaries and film uniformities among other parameters.     

小型太阳能发电系统与光伏建筑一体化

太阳能发电系统是利用光伏电池组件将太阳能直接转变为电能的一种装置。太阳能电池组件是利用半导体材料的电子学特性来实现P—V转换的一种固雄装置,在广大的无电力网地区,该装置可以方便地实现为用户照明及家用电器供电,某些发达国家还将其与区域电网并网实现互补。目前从民用的角度来看,在国外”光伏建筑一体化”的技术研究已趋于完善和成...     

金属氧化物半导体气敏材料的研究进展

金属氧化物是重要的半导体材料,具有较好的气敏特性,作为气敏材料被广泛应用。本文较系统地对金属氧化物气敏材料的研究现状作了阐述,重点介绍了复合氧化物气敏材料的研究状况,并对其气敏性质进行了概述。展望了金属氧化物半导体气敏材料今后的研究重点及发展方向。     

Research on double-barrier resonant tunneling effect based stress measurement methods

Piezoresistive effect of semiconductor materials is often used in microsensors as a sensing principle. Resonant tunneling diodes (RTDs) have been proved to have negative differential resistance effect, and their current–voltage characteristics change as a function of stress, which can be generated by external mechanical loads, such as pressures, accelerations and so on. According to this, the Meso-piezoresistive effect of RTDs can be used for stress measurement. This paper discusses two double-barrier resonant tunneling effect based stress measurement methods, including an RTD-Wheatstone bridge based method originally proposed. According to the results from the RTD-Wheatstone bridge based experiment, the piezoresistive sensitivity of RTD is adjustable in a range of 3 orders. And the largest piezoresistive sensitivity of RTD is larger than that of common semiconductor materials, such as silicon and GaAs.     

Wide bandgap semiconductor thin films for piezoelectric and piezoresistive MEMS sensors applied at high temperatures: an overview

The use of wide bandgap semiconductor thin films as sensing materials for micro-electrical–mechanical systems (MEMS) sensors has been the subject of much discussion in the academic and industrial communities. The motivation is that such materials are recognized as being suitable for extreme environment applications, namely: high temperatures, intense radiation and corrosive atmospheres. Among the wide bandgap semiconductor materials, aluminum nitride (AlN), zinc oxide (ZnO), diamond-like carbon (DLC) and silicon carbide (SiC) are highlighted due to their inherent sensing properties and compatibility with MEMS fabrication processes. Here we show an overview on the development technologies and applications of AlN, ZnO, DLC and SiC thin films in piezoelectric and piezoresistive MEMS sensors. Emphasis is placed on the influence of the temperature on the piezoelectric and piezoresistive properties of these films.     

浅谈化合物半导体材料

化合物半导体集成电路具有超高速、低功耗、多功能、抗辐射等特性而被和泛应用．GaAs、GaN、SiC为主要应用的化合物半导体材料。简单介绍化合物半导体材料和硅材料对比下的优势及由GaAs、GaN、SiC构成的部分器件的工作原理及特性。     

光伏充电控制器温度补偿的仿真研究

在光伏系统中,蓄电池的过充点保护电压应随外界环境温度和自身电解液温度的变化而变化,当过充点保护电压不变时,不但容易造成蓄电池的储电能力降低,而且严重时还会直接影响整个蓄电池的寿命。因此在光伏充电控制器中要添加温度补偿来降低因温度变化所造成的影响。根据蓄电池过充点保护电压随温度变化的客观规律,利用AD590温度传感器实现了充电控制器在充电过程中对过充点保护电压自动温度补偿的功能,从而提高了光伏系统的可靠性以及延长蓄电池的使用寿命。     

Analysis of interface states of metal–insulator–semiconductor photodiode with n-type silicon by conductance technique

A metal–insulator–semiconductor photodiode (MIS-PD) as active layer with n-type silicon as interdigitated Schottky electrodes has been fabricated. The current–voltage characteristics, density of interface states and photovoltaic properties of the MIS-PD diode have been investigated. The diode has a metal–insulator–semiconductor configuration with ideality factor higher than unity. The electronic parameters (ideality factor, series resistance and barrier height) of the diode were found to be 1.94, 2.23 × 10⁴ Ω and 0.74, respectively. At voltages between 0.13 and 0.50 V, the charge transport mechanism of the diode is controlled by space charge-limited current mechanism. The interface state density of the diode was found to vary from 5.54 × 10¹² to 5.67 × 10¹² eV⁻¹ cm⁻² with bias voltage. The Au/SiO₂/n-Si/Al device shows a photovoltaic behavior with a maximum open circuit voltage V_oc of 97.7 mV and short-circuit current I_sc of 17.4 μA under lower illumination intensities. The obtained electronic parameters confirm that the Au/SiO₂/n-Si/Al diode is a MIS type photodiode.     

NO_2气体传感器敏感材料

描述了近十年来用作NO2 气体传感器的酞菁类和氧化物半导体敏感材料。总结了这两类材料的成膜条件、薄膜表面形态和结构以及它们的敏感特性。为优化薄膜的气敏特性提供了参考     

纳米SnO_2的制备及其气敏特性分析

半导体纳米粒子应用于气敏材料是一新兴的研究领域,综述了ＳｎＯ２ 半导体超细化处理的研究进展。对各种制备方法作了详细描述,控制材料粒径的大小及粒度的分布、保证纳米团簇的稳定存在是纳米ＳｎＯ２ 制备的关键;分析了纳米ＳｎＯ２ 半导体材料的气敏特性,由于材料的比表面积增大、活性位增多,而具有着优异的气敏性能;并对其应用前景做出了进一步的展望。     

Integrated taste sensor using surface photovoltage technique

A surface photovoltage (SPV) technique has been applied to construct a taste sensor by combining modified LB (Langmuir-Blodgett) methods to immobilize taste-sensitive membranes. The contactless approach of the SPV method provides a simple sensing system with considerable patterning flexibility. Several kinds of artificial lipid membranes are monolithically integrated on a semiconductor surface as taste-sensitive materials and the surface potential change caused by the reactions with taste substances is detected by scanning a light beam along the semiconductor surface. First it is shown that the uniformly oriented lipid membranes exhibit different responses to five taste substances, with high sensitivity and fast response rate. Then, a preliminary experimental result to identify commercial drinks is demonstrated.     

Superlattices

The past decade has seen an explosive growth of interest in a new type of semiconductor called a superlattice. Made by sandwiching together thin layers of different semiconducting materials into a single crystal, a superlattice is a completely synthetic material. Superlattice properties such as the band gap may be tailored to suit particular applications, eg a laser whose output is tuned to suit optical fibres. Completely new devices such as a solid-state photomultiplier have been suggested and novel and unexpected physical phenomena have been observed.     

直拉硅单晶生长过程建模与控制研究综述

硅单晶是最重要的半导体材料,90%的半导体器件和集成电路芯片都制作在硅单晶上.随着集成电路技术的快速发展,对硅单晶的品质要求也不断提高.直拉法是生产硅单晶的主要方法,其科学原理与方法、生长技术与工艺、控制策略与手段一直是理论界和产业界高度关注和不断研究的热点.本文针对直拉法电子级硅单晶生长过程,以晶体生长基本原理为基础,从生长建模、变量检测、控制方法等方面进行了全面的阐述,特别针对当今大尺寸、高品质硅单晶生长的要求,总结了目前所取得的主要研究成果与面临的问题,并提出了相应的研究思路和方法.     

Artificial neural network-based modelling and fault detection of partial shaded photovoltaic modules

In this paper, a fault detection method for photovoltaic module under partially shaded conditions is introduced. It consists to use an artificial neural network in order to estimate the output photovoltaic current and voltage under variable working conditions. The measured data (solar irradiance, cell temperature, photovoltaic current and voltage) at Renewable Energy Laboratory REL, Jijel University (Algeria), have been used. The comparison between the estimated current and voltage with the ones measured gives useful information on the operating state of the considered photovoltaic module. To show the effectiveness of the proposed method, several shading patterns have been investigated. The results showed that the designed method accurately detects the shading effect on the photovoltaic module.     

n+n组合结构半导体丙酮气敏元件研究

n n组合结构半导体气敏元件是基于气敏元件互补反馈原理的一种新结构半导体气敏元件.该元件是由2种传导类型相同的敏感体A和B构成,A和B都是n型半导体材料.理论分析表明:当敏感体A和B满足一定条件时,该元件具有高的选择性,同时,还具有好的热稳定性和高的灵敏度.通过试验,获得了性能较好的n n组合结构丙酮气敏元件.     

材料基因方法在材料设计中的应用

【目的】本文主要介绍材料基因方法在一系列材料设计中的应用,如开发高性能催化材料、热电材料、金属有机框架(MOFs)材料、锂电池材料以及钙钛矿型光伏材料。【方法】将高通量计算与机器学习等数据挖掘技术结合,通过高通量计算产生一定规模的数据库,进而对材料数据库进行数据挖掘和分析。【结果】利用数据内在规律发现并筛选出潜在的新材料。【局限】目前,很多理论预测的材料在实验中合成制备还比较困难,因此理论与实验还需要更加深入地结合。【结论】随着计算机数据技术以及实验合成方法的进一步发展,材料基因方法将会在材料开发方面展现出更显著的作用。     

基于Pspice模拟行为模型的光伏阵列建模

根据光伏电池物理机制的数学表达式,利用Pspice仿真软件的模拟行为模型构建光伏电池的Pspice仿真模型.在此基础上,通过分析光伏阵列和光伏电池的关系及电路等效变换,建立任意功率级的PV仿真模型.该模型可以仿真任意太阳光照强度、环境温度、光伏模块参数及任意个光伏电池串并联组合下光伏阵列的I-V 、P-V特性.实验和仿真结果表明,仿真模型的输出特性与实际电池的输出特性基本一致,能较好体现光伏阵列的输出特性.模型的建立为光伏发电系统的动态仿真提供了有效的模拟输入电源.     

组合结构半导体气体传感器的研究进展

综合介绍了基于气体传感器互补反馈和互补增强原理的新型组合结构半导体气体传感器的研究进展,着重对传感器的原理、结构、材料及性能作了介绍,并分析了组合结构半导体气体传感器的发展趋势。     

Environmental gas sensing

Solid-electrolyte sensors for detecting air pollutants are urgently needed for the sake of environmental protection. Rapid progress is being marked in the development of sensors for CO₂, NO₂, NO, SO₂, ozone and fluorocarbons. Some of them, such as the CO₂ sensor, have almost reached a stage of practical application, while others are very promising. Most of these sensors have been fabricated with ceramic materials that are solid electrolytes and oxide semiconductors. The current status of research and development for air-pollutant sensing is described briefly.     

高k栅介质材料制备技术研究进展

随着半导体器件特征尺寸的不断减小,传统SiO2栅介质减薄到1nm以下时会导致栅极漏电流增大、器件可靠性下降等诸多问题,已无法满足CMOS技术长远发展要求。因此,寻求替代SiO2的新型栅介质材料,减少器件的隧穿电流,提升可靠性成为CMOS技术的发展方向。如何制备化学性质稳定、性能优异的栅介质薄膜成为高k栅介质材料亟待解决的问题。论述了理想高k栅介质材料的基本要求,重点介绍了高k栅介质材料制备技术的研究进展,并分析指出了高k栅介质材料制备技术的未来发展趋势。