XRD法计算4H-SiC外延单晶中的位错密度

对用X射线衍射法计算4H-SiC外延中的位错密度方法进行了理论和实验研究。材料中的位错密度大于106 cm-2会给材料位错密度的测试会带来一定的困难。首先从理论上分析了位错密度对X射线衍射结果的影响,得出位错密度和峰宽FWHM展宽的关系。然后对4H-SiC样品进行了X射线三轴晶ω-2θ测试,采用不同晶面衍射峰,计算出样品的位错密度。分析了外延中位错产生的原因,并提出了相应的解决办法。     

细胞色素BC1酶复合物抑制剂的对接研究

细胞色素BC1酶复合物是细胞呼吸和光合作用的重要组成部分,也是抑制病菌的重要靶标．细胞色素BC。酶复合物的抑制荆在近几年来的应用越来越广．为了得到活性更高的抑制剂,本文采用分子对接技术（DOCK4．0）,对8个典型结构的此类抑制剂进行了对接,并通过分析结合能与活性的相关性,得到了较好的构效关系模型,相关系数R^2=O．75．在此基础上,设计了4个新的抑制剂,均具有较高的预测活性．所建立的模型将为研究新的细胞色素BC。酶复合物抑制剂提供一定的理论指导．     

The fabrication of nickel silicide ohmic contacts to n-type 6H-silicon carbide

This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi硅化镍;欧姆触点;n型碳化硅;制造;能带;带隙Project supported by the National Basic Research Program of China (Grant No~2002CB311904), the National Defense Basic Research Program of China (Grant No~51327010101) and the National Natural Science Foundation of China (Grant No~60376001).2006-09-192006-10-30This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi2/SiC structure axe formed on N-wells created by N^＋ ion implantation into Si-faced p-type 6H-SiC epilayer respectively. NiSi and NiSi2 films are prepared by annealing the Ni and Si films separately deposited. A two-step annealing technology is performed for decreasing of oxidation problems occurred during high temperature processes. The specific contact resistance Pc of NiSi contact to n-type 6H-SiC as low as 1.78× 10^-6Ωcm^2 is achieved after a two-step annealing at 350 ℃for 20 min and 950℃ for 3 min in N2. And 3.84×10-6Ωcm^2 for NiSi2 contact is achieved. The result for sheet resistance Rsh of the N＋ implanted layers is about 1210Ω/□. X-ray diffraction analysis shows the formation of nickel silicide phases at the metal/n-SiC interface after thermal annealing. The surfaces of the nickel silicide after thermal annealing are analysed by scanning electron microscope.     

An optimized fitting function with least square approximation in InAs/AlSb HFET small-signal model for characterizing the frequency dependency of impact ionization effect

An enhanced small-signal model is introduced to model the influence of the impact ionization effect on the performance of In As/Al Sb HFET, in which an optimized fitting function D(ωτ_i) in the form of least square approximation is proposed in order to further enhance the accuracy in modeling the frequency dependency of the impact ionization effect.The enhanced model with D(ωτ_i) can accurately characterize the key S parameters of In As/Al Sb HFET in a wide frequency range with a very low error function EF. It is demonstrated that the new fitting function D(ωτ_i) is helpful in further improving the modeling accuracy degree.     

泡沫橡胶材料的超弹性本构模型

借助不可压橡胶类材料应变能函数,通过引入泡沫材料孔隙度,推导出了泡沫橡胶的本构方程。基于泡沫橡胶材料的单轴压缩实验结果,拟合确定了本构模型的参数,模型预测结果与实验结果吻合的比较好。     

The fabrication and characterization of 4H SiC power UMOSFETs

The fabrication of 4H-SiC vertical trench-gate metal-oxide-semiconductor field-effect transistors(UMOSFETs) is reported in this paper.The device has a 15-μm thick drift layer with 3×1015 cm-3 N-type doping concentration and a 3.1μm channel length.The measured on-state source-drain current density is 65.4 A/cm2 at Vg = 40 V and VDS = 15 V.The measured threshold voltage(Vth) is 5.5 V by linear extrapolation from the transfer characteristics.A specific on-resistance(Rsp-on) is 181 mΩ·cm2 at Vg = 40 V and a blocking voltage(BV) is 880 V(IDS = 100 μA@880V) at Vg = 0 V.     

向量优化问题中的弱S-有效解

在局部凸拓扑线性空间中, 提出了集值向量优化问题的弱S-有效解和S-次似凸性概念. 在S-次似凸性假设下建立了择一性定理, 并利用择一性定理建立了弱S-有效解的标量化定理. 此外, 通过几个具体例子解释了主要结果.     

非均匀局域共振型声子晶体隔声特性研究

建立局域共振声子晶体单元结构模型,通过有限元方法研究了阵列排布、填充率排列及散射体厚度排列对非均匀声子晶体隔声特性的影响,以期使各类非均匀声子晶体结构在不同频段发挥隔声效果及减少隔声频段内的局部衰减.结果表明,散射体靠近入射方向的阵列排布具有较大的隔声量;填充率由中间列向两端递增的形式下局部衰减情况较少;散射体厚度由中间列向两边减小的排布适合中高频隔声,由中间列向两边增大的排布适合低频隔声;分别由铝振子、钢振子、铅振子构成的声子晶体在低频段具有相似的隔声特性,中高频处的隔声频段随着振子密度的增加向低频段移动.此结果为非均匀声子晶体获得良好降噪效果提供了理论支持.     

向量优化问题 (C,\varepsilon)-弱有效解的一种非线性标量化性质

Guti\'{e}rrez 等在 co-radiant 集的基础上提出了一种新的 (C,\varepsilon)-弱有效解, 它统一了之前文献中提出的几种经典的近似解. 利用由 G\"{o}pfert 等提出的一类非线性标量化函数, 给出了 (C,\varepsilon)-弱有效解的一个等价性质. 最后, 给出一个例子说明主要结果.     

酰胺类酸性离子液体催化Oxa-Michael加成反应

设计合成并表征了N-甲基吡咯烷酮磷酸盐([NMPH]H2PO4)、己内酰胺磷酸盐([NHCH]H2PO4)、N,N'-二甲基甲酰胺磷酸盐([DMFH]H2PO4)和N,N'-二甲基乙酰胺磷酸盐([DMEH]H2PO4)等酰胺类质子酸离子液体;将其用于β-苯乙醇和丁烯酮的Oxa.Michael加成反应中,考察了离子液体阳...