Surface passivation in n-type silicon and its application in silicon drift detector

Based on the surface passivation of n-type silicon in a silicon drift detector(SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon(NAOS)method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition(PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate.The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×10¹⁵ cm^-3. When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA.     

反射波对预混气体爆炸过程与管壁动态响应的影响

为研究管道内甲烷/空气混合气体火焰和压力波的传播规律,对内载压力波作用下管壁的动态响应进行实验。结果表明,末端闭口实验中,管道末端的反射激波会引起当地火焰亮度的增大,而前端反射激波则有可能导致火焰内部的分离从而出现熄灭与复燃现象。相对于末端开口工况,末端闭口实验时管道两端产生的往复反射激波对管壁具有叠加加载作用,导致管壁产生较大的环向应变。     

Fe-MILs系可见光响应复合材料在光诱导反应中的应用研究进展

能源危机和环境问题已成为人类社会面临和亟待解决的两个重大问题。光催化技术被认为是解决能源危机和环境问题有效方法之一。来瓦希尔骨架材料（MILs）是一类著名的金属骨架有机材料（MOFs）。Fe-MILs是MILs系列材料中一个重要的分支,其带隙宽度约为2.39 eV ~ 2.79 eV,能被可见光激发。然而,Fe-MILs存在光的利用率低、导电性差、光生电子-空穴复合快、光腐蚀等缺点。近年来,研究者们采用多种方法对Fe-MILs进行改性,制备了很多Fe-MILs衍生的可见光响应复合材料,并将这些材料成功用于光诱导反应。本文主要综述了近年来Fe-MILs衍生的可见光响应复合材料在水的分解、CO2还原、有机物转化、光催化固氮等多个领域的应用研究,并对Fe-MILs光催化剂的发展提出了建议。     

粘土矿物参与微生物利用木质素形成矿物-菌体残留物的结构特征研究

粘土矿物在催化木质素形成腐殖质方面具有重要贡献。为有效阐明微生物-木质素-粘土矿物三者间的关系，探明矿物-菌体残留物的结构特征，采用液体摇瓶培养法，以木质素为碳源，通过添加高岭石和蒙脱石，在接种复合菌剂后启动110 d液体培养，期间动态收集矿物-菌体残留物，利用傅里叶红外光谱及扫描电子显微镜技术对其结构特性进行了研究。结果表明：高岭石颗粒边缘多由管状体卷曲而成，在参与微生物利用木质素形成矿物-菌体残留物后，连片状细小颗粒结构进一步团聚，结合更加紧凑，短管状结构增多，但整体仍保持多水高岭石的结构特征；在初始富营养条件下，高岭石能够促进微生物繁衍，使大量菌体聚集于高岭石表面，掩蔽了Si-O和Si-O-Al键，且矿物-菌体残留物中脂族碳结构比例增加；菌体中多糖物质通过含氧官能团与高岭石表面的水化层在多个部位形成氢键，氢键的形成对于高岭石稳定木质素及其降解产物具有重要作用，芳香碳结构比例和多糖类物质含量随培养时间逐渐增加，而后复合菌株对掩蔽在矿物表面的菌体进行二次利用，使高岭石Si-O-Al键重现；蒙脱石多由浑圆的颗粒结构组成，接种微生物可使其表面产生溶蚀，团粒结构遭到破碎；与10 d相比，历经30 d培养所得矿物-菌体残留物中的多糖类物质增多，使原本归属蒙脱石Si-O-Si及Si-O结构的1 034~1 038 cm-1处吸收峰强度增加，而后因多糖类物质与蒙脱石表面羟基发生缔合，又使该处吸收峰强度减弱，同时发生了氢键键合，该作用是蒙脱石-微生物-木质素间相互作用、形成矿物-菌体残留物的主要机制；高岭石在稳定有机碳方面的能力要高于蒙脱石，更易促进HS前体物质的形成。     

基于压电驱动器的风洞全模试验主动抑振研究进展

风洞全模试验是验证飞行器气动性能的重要试验。悬臂支杆作为该类型试验中最普遍采用的支撑方式,具有结构简单、安装方便、支撑干扰低等优点,但也存在支撑刚度低、结构阻尼小等特征,导致易出现模型支撑系统的振动。在大型风洞和低温风洞中此现象发生得尤为频繁,甚至中断吹风过程。针对该问题,首先对风洞全模测力试验振动问题的历史发展及传统振动抑制方法进行回顾,接着对风洞全模测力试验的振动问题进行分析,然后介绍了国内外的基于压电的各类抑振原理及抑振结构型式,并对主动抑振算法的研究进行了综述,最后总结了抑振系统对气动系数的影响,并讨论了攻角扩展的相关结果。     

端壁横向射流对高速扩压叶栅性能的影响

通过数值模拟研究了不同射流缝长度以及射流总压比对端壁横向射流抑制横向二次流动和减小损失作用效果的影响,结果表明:采用与流向具有一定夹角的横向射流可有效抑制端区二次流动,减少角区低能流体堆积,推迟吸力面流动分离,提高出口气流角均匀性。仅采用不足叶栅进口流量0.3%的射流气体,就能使总压损失系数降低11.3%。增加射流缝长度的或者提高射流总压均可增强其减弱分离流动的效果,但射流与横向二次流相互作用导致的冲击和掺混损失也增大。     

提高MIL-125(Ti)-NH2可见光催化活性的研究进展

太阳能是一种清洁的可再生能源,其中,可见光占太阳能总能量的45%。发展可见光响应的光催化剂是光催化领域重要的研究内容之一。NH₂-MIL-125（Ti）是一种有代表性的金属有机骨架可见光催化剂,但其存在可见光利用效率不高、光生电子-空穴对复合快等缺点。近年来,研究者们通过对NH₂-MIL-125（Ti）的晶面、结构和组成进行调控和修饰,提高其可见光催化活性。本文对近年来报道的关于提高NH₂-MIL-125（Ti）可见光催化活性的方法进行了综述,并对NH₂-MIL-125（Ti）基可见光催化剂的发展方向提出了建议,以期为NH₂-MIL-125（Ti）在光催化反应中进一步应用研究提供参考。     

Crystalline silicon surface passivation investigated by thermal atomic-layer-deposited aluminum oxide

Atomic-layer-deposited(ALD) aluminum oxide(Al_2O_3) has demonstrated an excellent surface passivation for crystalline silicon(c-Si) surfaces, as well as for highly boron-doped c-Si surfaces. In this paper, water-based thermal atomic layer deposition of Al_2O_3 films are fabricated for c-Si surface passivation. The influence of deposition conditions on the passivation quality is investigated. The results show that the excellent passivation on n-type c-Si can be achieved at a low thermal budget of 250℃ given a gas pressure of 0.15 Torr. The thickness-dependence of surface passivation indicates that the effective minority carrier lifetime increases drastically when the thickness of Al_2O_3 is larger than 10 nm. The influence of thermal post annealing treatments is also studied. Comparable carrier lifetime is achieved when Al_2O_3 sample is annealed for 15 min in forming gas in a temperature range from 400℃ to 450℃. In addition, the passivation quality can be further improved when a thin PECVD-SiN_x cap layer is prepared on Al_2O_3, and an effective minority carrier lifetime of2.8 ms and implied Voc of 721 mV are obtained. In addition, several novel methods are proposed to restrain blistering.     

Studies on the polycrystalline silicon/SiO_2 stack as front surface field for IBC solar cells by two-dimensional simulations

Interdigitated back contact(IBC) solar cells can achieve a very high efficiency due to its less optical losses. But IBC solar cells demand for high quality passivation of the front surface. In this paper, a polycrystalline silicon/SiO_2 stack structure as front surface field to passivate the front surface of IBC solar cells is proposed. The passivation quality of this structure is investigated by two dimensional simulations. Polycrystalline silicon layer and SiO_2 layer are optimized to get the best passivation quality of the IBC solar cell. Simulation results indicate that the doping level of polycrystalline silicon should be high enough to allow a very thin polycrystalline silicon layer to ensure an effective passivation and small optical losses at the same time. The thickness of SiO_2 should be neither too thin nor too thick, and the optimal thickness is 1.2 nm.Furthermore, the lateral transport properties of electrons are investigated, and the simulation results indicate that a high doping level and conductivity of polycrystalline silicon can improve the lateral transportation of electrons and then the cell performance.