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使用正电子湮没谱学方法,在不同气氛下对电化学腐蚀法制备的多孔硅中电子偶素的湮没行为进行了系统的研究.正电子湮没寿命谱测试结果表明,样品中存在长达40 ns的电子偶素湮没成分,并且进入多孔硅膜层的正电子约有80%形成电子偶素,具有非常高的电子偶素产额;在氧气气氛下,由于气体导致o-Ps发生自旋转化猝灭是使多孔硅样品中电子偶素寿命缩短的主要原因.结合正电子寿命-动量关联谱测量结果,分析了不同气氛下多孔硅样品中电子偶素湮没寿命及动量变化关系,讨论了多孔硅中电子偶素的湮没机理以及气氛对孔径计算理论模型的影响.
关键词:
电子偶素
正电子湮没谱学方法
多孔硅 相似文献
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采用电化学腐蚀制备多孔硅,利用场致发射扫描式电子显微镜(field emission scanning electron microscope,FESEM)观测多孔硅的二维微观形貌,利用Nano Indenter XP中的纳米轮廓扫描仪组件(nano profilometry, NP)得到其三维拓扑分析图像,分析了微观结构差异的原因并讨论了多孔硅内部微观结构对其机械性能的影响;利用MTS Nano Indenter XP纳米压入测量仪器,研究了多孔硅的显微硬度和杨氏模量随压入深度的变化规律,比较了不同孔隙率多孔硅的机械性能差别.实验结果测得40mA/cm2,60mA/cm2,80mA/cm2和100mA/cm2四个不同腐蚀电流密度条件下制备多孔硅样品的孔隙率在60%—80%范围内,孔隙率随着腐蚀电流密度的增加而增大;在氢氟酸(HF)浓度为20%的条件下制备出多孔硅样品的厚度在40μm—50μm范围内;测得多孔硅的平均硬度、平均杨氏模量分别在0.478GPa—1.171GPa和10.912GPa—17.15GPa范围内,并且其数值随腐蚀电流密度的增加而减小,在纳米硬度范围内随压入深度的增加而减小,在显微硬度范围内其数值保持相对恒定,分析了样品表面、厚度、微观结构,及环境对其机械性能的影响,得到了多孔硅力学性能随其微观尺度形貌的变化规律.
关键词:
多孔硅
微观结构
硬度
杨氏模量 相似文献
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本文报导了多孔硅的拉曼散射和光致发光的研究。给出了多孔硅的拉曼和光致发光谱之间的对应关系,根据拉曼峰的移动,估算了多孔硅量子线横截面的平均尺度为2.1~4.2nm。 相似文献
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在制备出光致发光能量为2.7eV的发射蓝光多孔硅的基础上对它进行了较系统的研究:测量了它的光致发光时间分辨光谱,用傅里叶交换红外光谱分析了其表面吸附原子的局域振动模,研究了γ射线辐照对其发光的影响,并与发红、黄光的多孔硅作了对比,通过空气中长期存放、激光和紫外线照射的方法,研究了光致发光峰能量为2.7eV的多孔硅发光稳定性.我们及其它文献中报道的多孔硅蓝光发射的实验结果与量子限制模型矛盾,但能用量子限制/发光中心模型解释.我们认为多孔硅的2.7eV发光是多孔硅中包裹纳米硅的SiOx层中某种特征发光中心引起的.
关键词: 相似文献
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用电化学方法制备了不发光多孔硅和发光多孔硅,用X射线双晶衍射对两类多孔硅表面进行了微结构分析和晶体质量表征,实验表明两类多孔硅的微结构间存在着很大差别。不发光多孔硅表面对X射线的双晶衍射摇摆曲线可解叠成两个峰,它们分别来自样品多孔层和单晶硅衬底,而发光多孔硅对X射线的双晶衍射摇摆曲线呈高斯对称分布,不可解叠。发光多孔硅比不发光多孔硅表面晶体质量差,且电化学腐蚀越严重,表面晶体质量下降也越严重。 相似文献
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用荧光光谱仪测量了多孔硅样品的任一给定点的荧光特性与激发波长的依赖关系, 发现当激发波长从650 nm变到340 nm时,该点的荧光谱峰位从780 nm连续蓝移到490 nm。用扫描电子显微镜(SEM)对多孔硅的截面进行了分析,结果显示多孔硅具有分形特性,这同作者的计算机模拟结果一致。结合多孔硅样品的激发光谱测量结果,多孔硅的荧光特性随激发波长改变的现象可以归因于多孔硅的分形结构以及量子尺寸效应。 相似文献
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G. Masini S. La Monica G. Maiello S. Lazarouk V. Bondarenko 《Il Nuovo Cimento D》1996,18(10):1205-1212
Summary Porous-silicon-based white-light-emitting devices are presented. The fabrication process on different substrates is described.
The peculiarities of technological steps for device fabrication (porous-silicon formation and aluminum treatment) are underlined.
Doping profile of the porous layer, current-voltage characteristics, time response, lifetime tests and electroluminescence
emission spectrum of the device are presented. A model for electrical behaviour of Al/porous silicon Schottky junction is
presented. Electroluminescence spectrum of the presented devices showed strong similarities with white emission from crystalline
silicon junctions in the breakdown region.
Paper presented at the III INSEL (Incontro Nazionale sul Silicio Emettitore di Luce), Torino, 12–13 October 1995. 相似文献
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P. K. Sadovskii A. R. Chelyadinskii V. B. Odzhaev M. I. Tarasik A. S. Turtsevich Yu. B. Vasiliev 《Physics of the Solid State》2013,55(6):1156-1158
A porous silicon layer as a getter of uncontrolled impurities has been prepared by implantation of Sb+ into silicon and subsequent thermal treatments. The lifetime of nonequilibrium charge carriers in n- and p-type silicon wafers with a getter layer is 3–4 times longer than that without a getter. 相似文献
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Pallab Banerji 《Applied Surface Science》2007,253(11):5129-5132
Atomic scale properties of thin porous silicon (PSi) layers, characterized by the formation of positronium, are investigated using positron annihilation lifetime spectroscopy in the temperature range 20-300 K under 10−7 Torr vacuum. The longest orthopositronium as well as the shortest parapositronium components are found to have quite low intensities in the thin layer at room temperature. It is also found that at temperatures ≤240 K, these two components do not show up in the spectrum. The reason for this absence of the longest lifetime component is suggested. 相似文献
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M. Ghrib M. GaidiT. Ghrib N. KhedherM. Ben Salam H. Ezzaouia 《Applied Surface Science》2011,257(21):9129-9134
Photoluminescence (PL) spectroscopy was used to determine the electrical band gap of nanocrystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous alumina structure by fitting the experimental spectra using a model based on the quantum confinement of electrons in Si nanocrystallites having spherical and cylindrical forms. This model permits to correlate the PL spectra to the microstructure of the porous aluminum silicon layer (PASL) structure. The microstructure of aluminum surface layer and nc-Si films was systematically studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). It was found that the structure of the nanocrystalline silicon layer (NSL) is dependent of the porosity (void) of the porous alumina layer (PAL) substrate. This structure was performed in two steps, namely the PAL substrate was prepared using sulfuric acid solution attack on an Al foil and then the silicon was deposited by plasma enhanced chemical vapor deposition (PECVD) on it. The optical constants (n and k as a function of wavelength) of the deposited films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV-vis-NIR regions. The SE spectrum of the porous aluminum silicon layer (PASL) was modeled as a mixture of void, crystalline silicon and aluminum using the Cauchy model approximation. The specific surface area (SSA) was estimated and was found to decrease linearly when porosity increases. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their micro-structural properties. 相似文献
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Zhihao Yue Honglie Shen Lei Zhang Bin Liu Chao Gao Hongjie Lv 《Applied Physics A: Materials Science & Processing》2012,108(4):929-934
In this paper, we present the result of heterojunction solar cells based on porous silicon layer transfer technology. a-Si/c-Si structured solar cells were prepared in which the c-Si was deposited on annealed double-layer porous silicon by low-pressure chemical vapor deposition. The structural properties and the evolvement of the double-layer porous silicon before and after thermal annealing were investigated by scanning electron microscopy. X-ray diffraction, Raman spectroscopy and a microwave photoconductive decay method were used to investigate the properties of the epitaxial silicon thin films deposited at different pressures. And, the influence of the deposition pressure on the properties of the c-silicon thin films was investigated. The spectral responses of the cells were studied by a quantum efficiency test. The results show that the epitaxial silicon thin film deposited at 100 Pa has better carrier lifetime and better spectral response. Furthermore, the Raman peak intensity of the silicon film prepared at 100 Pa is much closer to that of a monocrystalline silicon wafer. A simple solar cell structure without any light-trapping features showed an efficiency of up to 10.1 %. 相似文献
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S. Lebib H. J. von Bardeleben J. Cernogora J. L. Fave J. Roussel 《Journal of luminescence》1998,80(1-4):153-157
Porous Si1−xGex (PSiGe) layers with efficient room temperature visible photoluminescence (PL) were elaborated by anodical etching from p-type doped epitaxial layers with Ge contents from 5 to 30%. The luminescence is characterised by a broad PL band centred at 1.8 eV. Time resolved photoluminescence decay is studied in porous silicon germanium as a function of germanium content, temperature, emission energies and surface passivation. The PL decay line shape is well described by a stretched exponential in all cases. The effective lifetime at low temperature in as prepared porous Si1−xGex is 400 μs, i.e. an order of magnitude less than in porous silicon. After the formation of a 20 Å thick oxide surface layer we observe a decrease of the effective lifetime to 20 μs at T=4 K. 相似文献
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Chan Kok Sheng Wan Md. Zin Wan Yunus Anuar Kassim 《Physica B: Condensed Matter》2008,403(17):2634-2638
In this work, the porous silicon layer was prepared by the electrochemical anodization etching process on n-type and p-type silicon wafers. The formation of the porous layer has been identified by photoluminescence and SEM measurements. The optical absorption, energy gap, carrier transport and thermal properties of n-type and p-type porous silicon layers were investigated by analyzing the experimental data from photoacoustic measurements. The values of thermal diffusivity, energy gap and carrier transport properties have been found to be porosity-dependent. The energy band gap of n-type and p-type porous silicon layers was higher than the energy band gap obtained for silicon substrate (1.11 eV). In the range of porosity (50-76%) of the studies, our results found that the optical band-gap energy of p-type porous silicon (1.80-2.00 eV) was higher than that of the n-type porous silicon layer (1.70-1.86 eV). The thermal diffusivity value of the n-type porous layer was found to be higher than that of the p-type and both were observed to increase linearly with increasing layer porosity. 相似文献
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Masato Ohmukai Nobutomo Uehara Tetsuya Yamasaki Yasuo Tsutsumi 《Czechoslovak Journal of Physics》2004,54(7):781-784
We have investigated the effects of chemical etching on Raman spectra of porous silicon. The as-anodized porous silicon consisted
mainly of crystalline silicon, as indicated by the Raman spectra. The background in the spectrum was strong, indicating that
the porous silicon surface was rough due to the presence of pores. When chemical etching was performed five times, the Raman
spectrum revealed the presence of spherically shaped nanocrystalline silicon whose diameter was around 3.5 nm. Further chemical
etching, however, extinguished the nanocrystallites, in addition to smoothing the surface morphology. 相似文献
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V. M. Aroutiounian Kh. S. Martirosyan A. S. Hovhannisyan P. G. Soukiassian 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2008,43(2):72-76
Reflectance spectrum calculations of double- and triple-layer antireflection coatings made of porous silicon layer are performed, using the optical matrix approach method. Obtained results are compared with the reflectance spectrum of other type antireflection coatings. Lower reflectance value of both double- and triple-layer antireflection coatings made of porous silicon is obtained in comparison to that of SiO2/TiO2 antireflection coating. These results can be used in photovoltaic converters. 相似文献