Two-step method preparation of graphene without hydrogen on methanol pretreatment copper substrate by PECVD at low temperature

Plasma enhanced chemical vapor deposition (PECVD) is one effective method to prepare graphene at low temperature in a short time. However, the low temperature in PECVD could not provide substrate a proper state for large area and few layer graphene preparation. Herein, we propose a two-step method to grow graphene on Cu foils. In the first step, in order to acquire a smooth and oxide-free surface state, methanol was used as a reductant to pretreat Cu. In the second step, graphene films were prepared on Cu foils by PECVD using CH₄ as carbon source with H₂-free. Few-layer graphene sheets with diameter about 1 μm under low temperature (700 °C) and at a short time (10 min) on well pretreated Cu foils were successfully gotten. The effect of methanol pretreatment on graphene synthesis and the graphene growth mechanism on Cu substrate by PECVD are analyzed comprehensively.     

碳化硅扫描反射镜支撑结构设计

对尺寸为460 mm×290 mm的SiC扫描反射镜的轻量化和支撑结构的设计进行了研究。基于三角形和矩形的复合轻量化结构,采用镜体背部为开放和封闭相结合的形式,设计了一种新型的扫描反射镜组件。该组件采用侧面支撑方式和轴向柔性结构,有利于消除支撑结构材料热膨胀系数不匹配产生的热应力对镜面面形的影响。有限元方法分析结果表明：反射镜组件在1 g重力载荷和8℃温度变化作用下,反射镜镜面的面形误差RMS值分别为4.5 nm和20.3 nm。该反射镜轻量化形式和支撑结构满足光学成像要求,并可有效提高结构的稳定性,对于大尺寸反射镜组件的设计具有借鉴意义。     

Silicon heterojunction solar cell with amorphous silicon oxide buffer and microcrystalline silicon oxide contact layers

This Letter reports on the fabrication and characterization of silicon heterojunction solar cells with silicon oxide based buffer (intrinsic amorphous silicon oxide) and contact layers (doped microcrystalline silicon oxide) on flat p‐type wafers. The critical dependency of the cell performance on the front and rear buffer layer thickness reveals a trade‐off between the open circuit voltage V_oc and the fill factor FF. At the optimum, the highest efficiency of 18.5% (active area = 0.67 cm²) was achieved with V_oc = 664 mV, short circuit current J_sc = 35.7 mA/cm² and FF = 78.0%. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

碳化硅颗粒增强铝合金复合材料在不同条件下的磨损行为

动载磨损是工程应用的一种常见现象，然而已有的试验研究大都是以平稳加方式进行的，这样得到的磨损规律显然与实际工况下的不符。因此，利用滑动磨损和喷砂冲员两种不同的试验方法，对ＳｉＣ颗粒增强２０２４Ａｌ复合材料的磨损行为进行了试验研究。     

An optical study of the correlation between growth kinetics and microstructure of μc-Si grown by SiH4-H2 PECVD

Fully microcrystalline silicon, μc-Si, thin films have been deposited on corning glass by plasma enhanced chemical vapor deposition (PECVD) using SiH₄-H₂. The effects of the surface treatment and of the deposition temperature on microstructure of μc-Si films are investigated by “in situ” laser reflectance interferometry (LRI), “ex situ” spectroscopic ellipsometry (SE) and Raman spectroscopy. LRI indicated the existence of a “crystalline seeding time”, which is indicative of the crystallite nucleation, and depends on substrate treatments. Longer “crystalline seeding time” results in a lower density of crystalline nuclei, which grow laterally, yielding to complete suppression of the amorphous incubation layer and to growth of very dense, fully crystalline layer at a growth temperature as low as 120 °C.     

具有碳化硅纳米线编织结构的氧化铝泡沫陶瓷的制备及性能研究

本文利用简单、高效的浆料直接发泡法制备气孔率高达96%的Al₂O₃/Si泡沫陶瓷,并选用简便、易行的焦炭埋烧工艺在Al₂O₃/Si泡沫陶瓷坯体中生长出大量SiC纳米线。通过控制烧结温度来观察分析SiC纳米线的生长形貌变化。采用扫描电子显微镜(SEM)、X射线衍射仪、BET比表面积测试仪、电子万能试验机等对泡沫陶瓷的微观结构、物相组成、比表面积、气孔率、抗压强度、热导率进行分析与表征。结果表明,1 450 ℃烧结时得到的SiC纳米线最多,纳米线在泡沫陶瓷孔壁交织缠绕。同时观察到SiC纳米线的存在改变了氧化铝泡沫陶瓷固有的脆性断裂模式,SiC纳米线可有效促进泡沫陶瓷在压缩过程中的裂纹偏转。本实验制备了一种新型的纳米线缠绕在孔壁上的三维网络结构的泡沫陶瓷,为在泡沫陶瓷内部原位生长SiC纳米线提供了新的方法,更好地拓展了泡沫陶瓷在环境过滤、催化剂载体等领域中的应用。     

Complex investigation of multilayer nanostructure of a‐Si/SiO1.9 by probe and spectroscopic analysis techniques. Visualization of the band structure. Studying of the band structure of the suboxide border layers

This article describes an integrated approach to the study of multilayer nanostructures of a‐Si/SiO_1.9 as a potential model to study the influence of the effects arising at the interface of Si/SiO₂ under the influence of ionizing radiation. The results of the functional layers of amorphous silicon and silicon dioxide surface topology investigation have been disclosed. The possibility of application of a band gap contrast in electron probe studies by means of electron energy filtering during the detection process has been demonstrated. Changes in valence band and band gap through depth of the a‐Si/SiO_1.9 nanostructure have been registered. As part of the study, density of states of the a‐Si/SiO_1.9 multilayer nanostructures and depth distribution of surface suboxide layers of native oxide of amorphous silicon have been reconstructed using the determination of an effective mean free path of the electrons by the TPP2M algorithm in conjunction with PARXPS and REELS measurements. Copyright © 2015 John Wiley & Sons, Ltd.     

无紫外光照射下n型15R-SiC及6H-SiC晶体的电化学腐蚀

本文在无紫外光照射下通过电化学腐蚀法制备了多孔n型15R-及6H-SiC,并用扫描电子显微镜(SEM),拉曼散射及X射线衍射仪(XRD)对多孔层的结构进行了分析。结果表明:晶体的晶型及氧化条件等因素对多孔结构有较大影响。首次观察到多孔n型15-SiC的半圆管状结构,其孔隙率约是66%。     

氢氟酸刻蚀对Ni/6H-SiC接触性质的作用

采用浓度为10%的氢氟酸（HF）刻蚀6H-SiC单晶片,研究了HF刻蚀时间对Ni/6H-SiC接触性质的影响．经24?h刻蚀的SiC基片在溅射Ni层后,其接触表现良好线性的电流-电压（I-V）曲线．低于这个腐蚀时间的接触具有明显的势垒,但在大于1000℃快速退火后,也得到了良好线性的I-V曲线．X射线衍射（XRD）和俄歇能谱（AES）深度元素分析表明Ni₂Si和C是快速退火后的主要产物．XRD和低能反射电子能量损失谱表明表层的C 关键词： 欧姆接触 SiC 富碳层 互扩散     

VHF-PECVD沉积本征微晶硅薄膜激活能特性研究

采用激活能测试装置测量VHF-PECVD高速沉积的本征微晶硅薄膜,并对不同晶化率的样品和不同沉积功率、不同沉积压强条件下沉积制备的样品的激活能进行了分析研究.结果表明:在非晶-微晶相变域附近,激活能随着晶化率的升高而降低;随着沉积功率的增大和沉积气压的增大,沉积速率提高,样品的激活能升高,通过提高沉积功率和沉积气压可以有效的抑制氧污染.