Comparison of various buffer schemes to grow GaN on large-area Si(111) substrates using metal-organic chemical-vapor deposition

A comparison of gallium-nitride (GaN) films grown on large-area Si(111) using a single aluminum-nitride (AlN) buffer, an AlN/graded-Al_xGa_1−xN buffer, and the introduction of additional low-temperature (LT)-grown AlN interlayers is reported. A graded-AlGaN buffer followed by additional LT-AlN interlayers is shown to completely eliminate cracking in nitride films of thickness >2 μm and also reduce the threading-dislocation density significantly. A partial compensation of GaN-tensile strain by the compressive-lattice strain induced by the AlGaN and AlN layers is responsible for this effect. The surface roughness is increased by the introduction of the LT-AlN buffers.     

Structural properties of TiN films grown on stainless steel substrates by a reactive radio-frequency sputtering technique at low temperature

TiN thin films were grown on stainless steel substrates by using the reactive radio-frequency magnetron-sputtering technique at relatively low temperature (200°C) using Ti and N₂. The deposition rate of the TiN film increased linearly with increasing applied radio-frequency power, and it decreased with increasing partial-pressure ratio of the N₂ gas to the Ar gas. Scanning electron microscopy (SEM) showed that the surfaces of the TiN films had very smooth morphologies. The TiN thin film had good stoichiometry for a partial-pressure ratio of 0.05. The stoichiometry of the TiN films and the interface qualities of the TiN/stainless steel heterostructures were investigated by Auger electron spectroscopy (AES) measurements. Auger depth profiles indicated that the compositions of the as-grown films consisted of titanium and nitrogen uniformly distributed throughout the films and that the films exhibited smooth interfaces. The interface quality of the TiN films to the stainless steel substrates were improved by annealing. These results indicate that annealed TiN thin films grown on stainless steel substrates hold promise for potential applications in advanced ceramic devices.     

Pt薄膜热敏电阻工艺研究

本项研究目的是制作微型高精度铂薄膜热敏电阻器与集成电路配合,用于工业和科研中温度的精确测量。用高纯铂板作靶材,在玻璃基板上采用磁控溅射方法,制备成Pt薄膜热敏电阻,并在两端制作纯金电极。经测试表明,该Pt薄膜热敏电阻具备良好的线性度和灵敏度,电阻温度系数达到(或接近)3 850 ?06℃1。本工艺条件稳定,适合批量生产。     

Multiplex SERS Detection of Metabolic Alterations in Tumor Extracellular Media

The composition and intercellular interactions of tumor cells in the tissues dictate the biochemical and metabolic properties of the tumor microenvironment. The metabolic rewiring has a profound impact on the properties of the microenvironment, to an extent that monitoring such perturbations could harbor diagnostic and therapeutic relevance. A growing interest in these phenomena has inspired the development of novel technologies with sufficient sensitivity and resolution to monitor metabolic alterations in the tumor microenvironment. In this context, surface‐enhanced Raman scattering (SERS) can be used for the label‐free detection and imaging of diverse molecules of interest among extracellular components. Herein, the application of nanostructured plasmonic substrates comprising Au nanoparticles, self‐assembled as ordered superlattices, to the precise SERS detection of selected tumor metabolites, is presented. The potential of this technology is first demonstrated through the analysis of kynurenine, a secreted immunomodulatory derivative of the tumor metabolism and the related molecules tryptophan and purine derivatives. SERS facilitates the unambiguous identification of trace metabolites and allows the multiplex detection of their characteristic fingerprints under different conditions. Finally, the effective plasmonic SERS substrate is combined with a hydrogel‐based three‐dimensional cancer model, which recreates the tumor microenvironment, for the real‐time imaging of metabolite alterations and cytotoxic effects on tumor cells.     

Effect of temperature on elastic properties of woven-glass epoxy composites for printed circuit board applications

The effect of temperature on the elastic properties of woven-glass epoxy substrates for printed circuit board applications was investigated. Three common commercially pressed boards (1080, 2116, and 7628 woven-glass fabrics and FR4 epoxy) were used for this study. The elastic properties were identified by means of a combined theoretical and experimental vibration method. Vibration experiments were performed under reduced air pressure to reduce the influence of mass, stiffness, and damping of the surrounding air and inside an environmental chamber with varying temperature and constant humidity. Above the glass-transition temperature (Tg) of the epoxy, the in-plane shear moduli (G₁₂) were decreased by 33–37% and the out-of-plane shear moduli (G₁₃, G₂₃) were decreased by 48%, whereas the Young’s moduli in the warp (E₁) and fill (E₂) directions were much less affected.     

EBSD技术在第二代高温超导涂层导体研究中的应用

本文利用EBSD技术研究涂层导体用的第二代高温超导镍钨合金基带的显微组织、平均晶粒尺寸、各织构组分含量、取向差分布和特殊晶界(CSL)等.并通过EBSD技术获得缓冲层的显微组织、旋转立方织构含量.     

KA波段模拟移相器的仿真设计

利用ADS2009仿真并设计了一种KA波段模拟移相器,其工作频段为19.6~21.2 GHz,工作带宽为1.6 GHz。在设计中采用skyworks公司的SMV2019变容二极管,以砷化镓陶瓷基片作为基板,金属金作为微带线的导体材料,并在设计中采用馈电分支线耦合器电桥模式,最终设计出一款最大移相能力为105.226°的连续可调的压控模拟移相器。     

GaSb基的InAs/GaSbⅡ类超晶格背景载流子浓度的测量

高质量的InAs/GaSbⅡ类超晶格(SLs)材料生长在晶格匹配的GaSb衬底上,由于GaSb衬底具有良好的导电性,传统的霍尔测量难以直接得到外延超晶格材料的载流子浓度等电学参数,所以,如何准确地获得InAs/GaSb超晶格外延材料中的载流子浓度成为了研究人员关注的焦点之一。主要介绍了InAs/GaSbⅡ类超晶格背景载流子浓度测量的四种典型的方法:低温霍尔技术;变磁场霍尔技术以及迁移率谱拟合;衬底去除技术;电容-电压技术。并给出了各种方法的基本原理,评价了每种方法的优缺点。     

Chemical Sensing Systems that Utilize Soft Electronics on Thin Elastomeric Substrates with Open Cellular Designs

A collection of materials and device architectures are introduced for thin, stretchable arrays of ion sensors that mount on open cellular substrates to facilitate solution exchange for use in biointegrated electronics. The results include integration strategies and studies of fundamental characteristics in chemical sensing and mechanical response. The latter involves experimental measurements and theoretical simulations that establish important considerations in the design of low modulus, stretchable properties in cellular substrates, and in the realization of advanced capabilities in spatiotemporal mapping of chemicals' gradients. As the chemical composition of extracellular fluids contains valuable information related to biological function, the concepts introduced here have potential utility across a range of skin‐ and internal‐organ‐integrated electronics where soft mechanics, fluidic permeability, and advanced chemical sensing capabilities are key requirements.     

TiO_2粒径对聚四氟乙烯/TiO_2复合材料性能的影响

采用热压烧结工艺制备了TiO2陶瓷填充聚四氟乙烯(PTFE)复合基板材料。系统研究了TiO2陶瓷粒径对PTFE/TiO2复合材料显微结构、热导率、微波介电性能的影响。结果表明,复合材料的密度随TiO2粒径的增大而增大,而介电损耗、吸水率则随着TiO2粒径的增大而减小;相对介电常数和热导率随粒径的增大先减小,当TiO2粒径D50为6.5μm时达到最小值,然后开始增大。当TiO2的粒径D50为11μm时,复合材料具有较高的相对介电常数(εr=6.8),较低的介电损耗(tanδ=0.001 2)和较高的热导率(0.533 W/(m·℃))。