基于压敏漆的带横槽气膜冷却实验与数值研究

为改善燃气轮机高温透平叶片的设计,使用压力敏感漆实验技术和数值方法对平板气膜冷却进行对比研究,分析了0°、45°和90°复合角时,有无横槽结构对圆孔气膜冷却的影响。结果表明有复合角时横槽结构能显著提高气膜冷却效率,因为横槽壁对射流形成阻碍作用,在横槽内形成侧向涡,加强了由复合角引起的射流侧向动量。     

一种钢管混凝土格构柱极限承载力的快速计算方法

采用半波正弦曲线模拟杆件的变形曲线,在考虑紧箍效应钢管混凝土应力-应变关系和剪切变形影响的基础上,建立了杆件中截面的平衡方程,提出了钢管混凝土格构柱弹塑性极限承载力数值方法,并编制了相应的计算程序。该方法不仅适用于两端偏心相等的偏压构件及两端偏心不等的偏压构件的弹塑性极限承载力的计算,而且,其收敛速度很快,比分段合成数值法更能适用于工程计算。利用提出的计算方法和编制的程序对国内已有两端偏心相同的四肢钢管混凝土格构偏压长柱的试验结果进行了计算,并与现有规程及分段合成法进行了比较,结果表明:规程计算方法结果偏于保守,计算误差大,本文方法的计算结果与试验结果吻合良好。     

钢管混凝土K型相贯节点试验研究与数值模拟

从钢管混凝土格构式风电塔架原型中取出节点模型,对5个K型焊接相贯节点进行了试验研究和理论分析,研究了不同几何参数条件下节点的破坏过程和特征、荷载-变形关系和承载能力等。建立了有限元模型,分析了各研究参数对节点破坏形态和极限承载力的影响规律,得到了节点失效机制的判别参数与准则。试验结果表明:圆钢管混凝土K型相贯节点在丧失承载力前弦杆的宏观变形特征不明显,腹杆失效是主要破坏形态;与空心圆钢管相贯节点相比,刚度大大增加,相贯线周围应力集中程度也降低。有限元分析结果表明:圆钢管混凝土K型相贯节点的控制破坏形态包括腹杆失效和弦杆冲剪破坏,控制破坏类型的关键指标是腹杆与弦杆的壁厚比τ和夹角θ。为避免钢管混凝土格构式风电塔架出现节点失效,须限制参数τ、θ的取值。本文建议τ≤1,θ≤45°。     

U型槽刻蚀工艺对GaN垂直沟槽型金属-氧化物-半导体场效应晶体管电学特性的影响

U型槽的干法刻蚀工艺是GaN垂直沟槽型金属-氧化物-半导体场效应晶体管(MOSFET)器件关键的工艺步骤,干法刻蚀后GaN的侧壁状况直接影响GaN MOS结构中的界面态特性和器件的沟道电子输运.本文通过改变感应耦合等离子体干法刻蚀工艺中的射频功率和刻蚀掩模,研究了GaN垂直沟槽型MOSFET电学特性的工艺依赖性.研究结果表明,适当降低射频功率,在保证侧壁陡直的前提下可以改善沟道电子迁移率,从35.7 cm^2/(V·s)提高到48.1 cm^2/(V·s),并提高器件的工作电流.沟道处的界面态密度可以通过亚阈值摆幅提取,射频功率在50 W时界面态密度降低到1.90×10^12 cm^-2·eV^-1,比135 W条件下降低了一半.采用SiO2硬刻蚀掩模代替光刻胶掩模可以提高沟槽底部的刻蚀均匀性.较薄的SiO2掩模具有更小的侧壁面积,高能离子的反射作用更弱,过刻蚀现象明显改善,制备出的GaN垂直沟槽型MOSFET沟道场效应迁移率更高,界面态密度更低.     

Complete filling of 41 nm trench pattern using Cu seed layer deposited by SAM-modified electroless plating and electron-beam evaporation

To overcome the limitation of the sputtered Cu seed layer in electroplating of Cu interconnects imposed by the shadow effect, a new method for depositing a Cu seed layer on a 41 nm trench pattern based on combination of electroless plating (ELP) and electron-beam (E-Beam) evaporation was developed. A Cu seed layer formed by ELP alone was too thin to be used for electroplating due to its high resistivity. To solve this problem, an additional Cu layer was deposited on top of the trench by E-Beam evaporator to enhance the electrical conductivity of the Cu seed layer. The electrical resistivity of the resulting Cu layer was reduced to 4.8 μΩ cm, which was sufficient for the conductive seed layer for electroplating the 41 nm trench pattern. The gap-filling capability also improved and there were no voids or seams in the 41 nm trench pattern. The proposed method can be an effective solution for fabrication of a conductive seed layer to fill a 41 nm trench pattern by electroplating.     

Effects of under‐relaxation factors on turbulent flow simulations

Under‐relaxation factors are significant parameters affecting the convergence of a numerical scheme. Some earlier work has been done to optimize these parameters, but this was restricted to special flow domains, and the range of changes for under‐relaxation factors and convective algorithms are limited. In this paper, the effects of changing under‐relaxation factors for different variables, different convective schemes and grid sizes on the convergence of the numerical solution of three 2D turbulent flow situations are studied. These three flows are duct flow, trench flow and inclined free falling jet flow. Copyright © 2003 John Wiley & Sons, Ltd.     

基于弹性变形理论的钢管混凝土短柱承载力计算理论研究

为解决工程中得到广泛应用的钢管混凝土结构承载力计算问题,在总结分析已有钢管混凝土短柱承载力计算理论的基础上,利用弹性变形理论,推导出了钢管混凝土短柱极限承载力计算公式,利用推导得出的计算公式,对混凝土的泊松比趋近于零、混凝土的弹性模量趋近于零、钢管和混凝土的弹性模量和泊松比都相等、钢管和混凝土的泊松比相等而其弹性模量不等、钢管混凝土短柱端面上混凝土凸出或凹进的影响等六种条件下,钢管混凝土结构的承载情况进行了分析.     

具有纵向漏极场板的低导通电阻绝缘体上硅横向双扩散金属氧化物半导体器件新结构

为降低绝缘体上硅(SOI)横向双扩散金属氧化物半导体(LDMOS)器件的导通电阻,同时提高器件击穿电压,提出了一种具有纵向漏极场板的低导通电阻槽栅槽漏SOI-LDMOS器件新结构.该结构特征为采用了槽栅槽漏结构,在纵向上扩展了电流传导区域,在横向上缩短了电流传导路径,降低了器件导通电阻;漏端采用了纵向漏极场板,该场板对漏端下方的电场进行了调制,从而减弱了漏极末端的高电场,提高了器件的击穿电压.利用二维数值仿真软件MEDICI对新结构与具有相同器件尺寸的传统SOI结构、槽栅SOI结构、槽栅槽漏SOI结构进行了比较.结果表明:在保证各自最高优值的条件下,与这三种结构相比,新结构的比导通电阻分别降低了53%,23%和提高了87%,击穿电压则分别提高了4%、降低了9%、提高了45%.比较四种结构的优值,具有纵向漏极场板的槽栅槽漏SOI结构优值最高,这表明在四种结构中新结构保持了较低导通电阻,同时又具有较高的击穿电压.     

具有L型源极场板的双槽绝缘体上硅高压器件新结构

为了提高小尺寸绝缘体上硅(SOI)器件的击穿电压,同时降低器件比导通电阻,提出了一种具有L型源极场板的双槽SOI高压器件新结构.该结构具有如下特征:首先,采用了槽栅结构,使电流纵向传导面积加宽,降低了器件的比导通电阻;其次,在漂移区引入了Si O2槽型介质层,该介质层的高电场使器件的击穿电压显著提高;第三,在槽型介质层中引入了L型源极场板,该场板调制了漂移区电场,使优化漂移区掺杂浓度大幅增加,降低了器件的比导通电阻.二维数值仿真结果表明:与传统SOI结构相比,在相同器件尺寸时,新结构的击穿电压提高了151%,比导通电阻降低了20%;在相同击穿电压时,比导通电阻降低了80%.与相同器件尺寸的双槽SOI结构相比,新结构保持了双槽SOI结构的高击穿电压特性,同时,比导通电阻降低了26%.     

Utilizing a shallow trench isolation parasitic transistor to characterize the total ionizing dose effect of partially-depleted silicon-on-insulator input/output n-MOSFETs

We investigate the effects of 60 Co γ-ray irradiation on the 130 nm partially-depleted silicon-on-isolator(PDSOI)input/output(I/O) n-MOSFETs. A shallow trench isolation(STI) parasitic transistor is responsible for the observed hump in the back-gate transfer characteristic curve. The STI parasitic transistor, in which the trench oxide acts as the gate oxide,is sensitive to the radiation, and it introduces a new way to characterize the total ionizing dose(TID) responses in the STI oxide. A radiation enhanced drain induced barrier lower(DIBL) effect is observed in the STI parasitic transistor. It is manifested as the drain bias dependence of the radiation-induced off-state leakage and the increase of the DIBL parameter in the STI parasitic transistor after irradiation. Increasing the doping concentration in the whole body region or just near the STI sidewall can increase the threshold voltage of the STI parasitic transistor, and further reduce the radiation-induced off-state leakage. Moreover, we find that the radiation-induced trapped charge in the buried oxide leads to an obvious front-gate threshold voltage shift through the coupling effect. The high doping concentration in the body can effectively suppress the radiation-induced coupling effect.