第二类超导体输运临界电流密度的一个临界态模型计算

给出了第二类超导体临界电流密度随样品尺寸及外加磁场变化的一个临界态模型计算。计算中考虑了样品中混合态与迈斯纳态共存的情况。用该模型对Tl2Ba2Ca2Cu3O10样品的实验测量结果进行了模拟计算,并讨论了有关问题。     

Forward and reverse electron transport properties across a CdS/Si multi-interface nanoheterojunction

The electron transport behavior across the interface plays an important role in determining the performance of op- toelectronic devices based on heterojunctions. Here through growing CdS thin film on silicon nanoporous pillar array, an untraditional, nonplanar, and multi-interface CdS/Si nanoheterojunction is prepared. The current density versus voltage curve is measured and an obvious rectification effect is observed. Based on the fitting results and model analyses on the forward and reverse conduction characteristics, the electron transport mechanism under low forward bias, high forward bias, and reverse bias are attributed to the Ohmic regime, space-charge-limited current regime, and modified Poole-Frenkel regime respectively. The forward and reverse electrical behaviors are found to be highly related to the distribution of inter- facial trap states and the existence of localized electric field respectively. These results might be helpful for optimizing the preparing procedures to realize high-performance silicon-based CdS optoelectronic devices.     

蓝光发射多孔硅RTO过程中的尺寸分离效应

对用水热腐蚀技术制备的、具有蓝光发射的多孔硅样品在快速热氧化(RTO)处理前后其光致发光谱、硅纳米颗粒的大小及尺寸分布变化进行了研究.实验发现,新鲜多孔硅样品经过RTO处理后,其光致发光谱整体蓝移并由单发光峰分裂为两个发光峰;与此对应,样品中的硅纳米颗粒在整体减小的同时出现尺寸分离现象.这一结果表明,多孔硅中的短波长发射也具有强烈的尺寸相关性. 关键词：     

硅纳米孔柱阵列及其四氧化三铁复合薄膜的湿敏电容特性研究

报道了硅纳米孔柱阵列（Si-NPA），Fe₃O₄复合的Si-NPA（Fe ₃O₄/Si-NPA）两种薄 膜材料的制备方法并对其形貌和结构进行了表征，研究了其电容湿度传感特性.结果表明，S i-NPA，Fe₃O₄/Si-NPA均为微米/纳米结构复合体系.当环境相对湿 度从11％上升到95％ 时，采用100 Hz的信号频率进行测试，以Si-NPA和Fe₃O₄/Si-NPA 为电介质材料制成的湿 敏元件的电容增加值分别为起始值的1500％和5500％；采用1000 Hz的信号频率测试时，则 分别为起始值的800％和12000％，显示出两种材料较高的湿度灵敏性和较强的绝对电容输出 信号强度.同时，在升湿和降湿过程中，Si-NPA，Fe₃O₄/Si-NPA都 具有较快的响应速度 ，其响应时间分别为15 s，5 s和20 s，15 s.文章结合材料的形貌和结构特性对其物理机理 进行了分析.上述结果表明，Si-NPA无论是直接作为湿度薄膜传感材料还是作为复合薄膜湿 度传感材料的衬底都具有很好的前景. 关键词： 硅纳米孔柱阵列 3O₄')" href="#">Fe₃O₄ 湿度电容传感特性     

发光不衰减的多孔硅

用一种新的方法制备出了具有不同衰减的光致发光特性的多孔硅。如此制备的多孔硅新鲜样品,其发光峰位强度比普通多孔硅高２￣２．５倍,将样品在室温下暴露于空气中,其发光强度在前４个月中单调增加,然后达到饱和。在随后的８个月中,没有观察到发光衰减,发光峰位也没有发生变化,这种发光稳定性被归因子于多孔硅表面所形成的稳定的Ｆｅ－Ｓｉ键。文章探讨了发光不衰减、峰位不蓝移的机理,并为多孔硅发光的量子限域模型提供了强     

Pressure-induced enhancement of optoelectronic properties in PtS_2

PtS_2, which is one of the group-10 transition metal dichalcogenides, attracts increasing attention due to its extraordinary properties under external modulations as predicted by theory, such as tunable bandgap and indirect-to-direct gap transition under strain; however, these properties have not been verified experimentally. Here we report the first experimental exploration of its optoelectronic properties under external pressure. We find that the photocurrent is weakly pressuredependent below 3 GPa but increases significantly in the pressure range of 3 GPa–4 GPa, with a maximum ～ 6 times higher than that at ambient pressure. X-ray diffraction data shows that no structural phase transition can be observed up to26.8 GPa, which indicates a stable lattice structure of PtS_2 under high pressure. This is further supported by our Raman measurements with an observation of linear blue-shifts of the two Raman-active modes to 6.4 GPa. The pressure-enhanced photocurrent is related to the indirect-to-direct/quasi-direct bandgap transition under pressure, resembling the gap behavior under compression strain as predicted theoretically.     

无电镀沉积于硅衬底上铜纳米晶的场发射性能

采用无电镀沉积技术在经过机械抛光的单晶硅衬底上沉积了铜纳米晶.利用X射线衍射数据,估算出所沉积铜纳米晶的平均粒径大约为40nm.对120s无电镀沉积样品的场发射测试表明,该样品的开启场强为～5.5V/μm,在场强达到9.26V/μm时的场发射电流密度可达到62.5μA/cm2.对相应的沉积过程和场发射机理进行了分析.结果表明,无电镀沉积技术有可能成为制备具有较好场发射性能的金属/硅冷阴极的一种可供选择的方法.     

以硅纳米孔柱阵列为模板制备金纳米薄膜

采用浸渍技术,分别以新鲜和老化两组硅纳米孔柱阵列(Si-NPA)衬底为模板制备了不同形貌特征的Au/Si-NPA.结果表明:造成两组衬底上形成的Au/Si-NPA形貌上的巨大差异主要是由于两组Si-NPA衬底表面氧含量的分布不同所致.进一步分析发现,Si-NPA在Au/Si-NPA的形成过程中既起到了模板作用,又起到了还原的双重作用.由于Si-NPA具有规则的阵列结构,从而使得金在Si-NPA表面上的沉积速率产生选择性,最终可以形成准周期的、规则的金纳米复合薄膜.     

银在硅纳米孔柱阵列上浸渍沉积的位置选择性

利用硅纳米孔柱阵列(Si-NPA)表面规则的图案化形貌和还原性,采用浸渍沉积技术制备了具有三种不同表面结构特征的Ag/Si-NPA复合纳米体系.在未经清洗的Si-NPA衬底,沉积银的形貌为树枝状;在新鲜衬底和自然老化衬底上,银的沉积都会形成规则的手链网络;而经过强氧化处理的衬底上则不能实现银的浸渍沉积.分析表明,Si-NPA表面的规则阵列和多孔结构等几何构型,在样品的后处理过程中将导致样品表面氧化程度随空间几何位置出现周期性梯度分布,从而对浸渍溶液中银离子在不同几何特征区域的还原、成核及生长模式产生控制作用,最终导致了银在Si-NPA表面浸渍沉积的位置选择性.本研究为采用浸渍沉积技术制备周期性、图案化的金属/硅复合纳米体系,研究其物理性能并探索其可能的器件应用奠定了基础.     

Photocatalytic Properties of TiO2/Si-NPA Nano Composite Systems

A new composite system is fabricated by depositing the TiO2 film on a silicon nanoporous pillar array （Si-NPA） and annealing at 500℃ using the spin coating method. Such a composite system exhibits a uniform morphology with the micron-dimension pillar array. Photocatalytic properties are investigated based on the degradation of methyl orange dye solution, and the results show that the photocatalytic efficiency of such a nano-composite system is 1.7 times that of the TiO2/glass system. The enhancement of photocatalytic efficiency is attributed to the large surface area of the TiO2/Si-NPA system.