共查询到20条相似文献,搜索用时 31 毫秒
1.
Guanghong Wang Chengying Shi Xuewei Cao Hui Wang Min Feng Jianmin Hao Yufang Wang 《Solid State Communications》2008,146(9-10):409-411
We report the formation of porous n-type 15R- and 6H-SiC and analyze the porous layers using scanning electron microscopy, Raman scattering and X-ray diffraction (XRD). The crystal structures and the preparation conditions of porous SiC are shown to have an effect on the structural and electrical properties of the material obtained. Raman spectra of porous SiC layers have shown some specific features compared with those of bulk SiC. For the porous 15R-SiC, the semi-cylindrical structure of the porous network has been observed and the porosity is about 66%. 相似文献
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1D-nanostructural zinc oxide (ZnO) with different shapes have been synthesized on p-type Si(1 0 0) and glass substrates via vapor phase growth by heating pure zinc powder at temperatures between 480 and 570 °C. The different ZnO nanostructures depend on the substrates and the growth temperatures. Scanning electron microscopy and X-ray diffraction revealed that a well-aligned nanowires array, which are vertical to the substrate of Si(1 0 0) with 18 sides on their heads, but six sides on their stems, has been formed at 480 °C. Raman study on the ZnO nanostructures shows that the coupling strength between electron and phonon determined by the ratio of the second- to the first-order Raman scattering cross-sections declines with decreasing diameter of the nanowires. However, a little changes of the coupling strength in terms of the width of the nanobelts have been observed. 相似文献
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V. Ya. Bratus'' M. Ya. Valakh I. P. Vorona T. T. Petrenko V. A. Yukhimchuk P. L. F. Hemment T. Komoda 《Journal of luminescence》1998,80(1-4):269-273
Thermally grown SiO2 layers on Si substrates implanted with Si+ ions with a dose of 6×1016 cm−2 were studied by the techniques of photoluminescence, electron paramagnetic resonance (EPR), and low-frequency Raman scattering. Distinct oxygen-vacancy associated defects in SiO2 and non-bridging oxygen hole centers were identified by EPR. The luminescence intensity in the 620 nm range was found to correlate with the number of these defects. The low-frequency Raman scattering technique was used to estimate the average size of the Si nanocrystallites formed after the implantation and thermal annealing at T>1100°C, which are responsible for the photoluminescence band with a maximum at 740 nm. The intensity of this band can be significantly enhanced by an additional treatment of the samples in a low-temperature RF plasma. 相似文献
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《Journal of luminescence》1998,80(1-4):183-186
Porous Si layers of different thicknesses were prepared by anodising p+-type Si substrates with a resistivity of 0.01 Ω cm. The porosity of the samples ranged from 23% to 62%. The refractive index values for the ordinary and extraordinary rays were determined by multiple angle of incidence ellipsometry, from which an optical anisotropy parameter varying from 13% to 20% was obtained. The porous Si layers were modelled as uniaxially anisotropic films on an isotropic substrate, with an optical axis perpendicular to the sample surface. The morphological anisotropy which is typical for the p+-type porous Si with a predominating cylindrical geometry is responsible for these optical properties. All the porous Si layers studied were found to be optically negative. 相似文献
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The thermal effects produced by continuous-wave laser radiation on free-standing Si/SiO2 superlattices are studied. We compare two samples with different SiO2 layer thicknesses (2 and 6 nm) and the same Si layer thickness (2 nm). The as-prepared free-standing superlattices contain
some amount of Si nanocrystals (Si-nc). Intense laser irradiation at 488 nm of the as-prepared samples enhances the Raman
scattering of Si-nc by two orders of magnitude. This laser-induced crystallization originates from melting of Si nanostructures
in silica, which makes Si-nc better ordered and better isolated from the oxide surrounding. Continuous-wave laser control
of Si-nc stress was achieved in these samples. In the proposed model, intense laser radiation melts Si-nc, and Si crystallization
upon cooling down from the liquid phase in a silica matrix leads to compressive stress. The Si-nc stress can be tuned in the
∼3 GPa range using laser annealing below the Si melting temperature. The high laser-induced temperatures were verified with
Raman spectroscopy. The laser-induced heat leads to a strongly nonlinear rise of light emission. The light emission is also
observed in the anti-Stokes region, and its temperature dependence is practically the same for the two studied samples. The
laser-induced temperature is essentially controlled by the absorbed laser power.
PACS 78.55.-m; 78.20.-e; 68.55.-a; 78.30.-j 相似文献
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采用溶胶凝胶法在Si(001)基片上制备铁电铌酸锶钡薄膜,使用X射线衍射、摇摆曲线、扫描电子显微镜、喇曼散射光谱等测试手段研究薄膜的微结构与薄膜厚度之间的关系,制备的薄膜厚度可达到5μm.实验发现,随着薄膜厚度的增加,SBN60和SBN75薄膜在(001)方向的优先取向性越来越好.随着膜层的增加,处于底层的膜层能够起到缓冲层的作用,以逐渐改善薄膜与基片之间的晶格失配,从而使得晶体的结晶取向性越来越好. 相似文献
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T. M. Burbaev A. A. Gorbatsevich V. I. Egorkin I. P. Kazakov V. P. Martovitskii N. N. Mel’nik Yu. A. Mityagin V. N. Murzin S. A. Savinov S. S. Shmelev 《Bulletin of the Lebedev Physics Institute》2013,40(8):219-224
The results of the comprehensive study of LT-GaAs epitaxial structures on GaAs and Si substrates by high-energy electron diffraction, reflection anisotropy spectroscopy, atomic force microscopy, X-ray diffraction, Raman scattering, and photoluminescence methods are presented. The results obtained indicate the existence of several channels of nonequilibrium carrier recombination, which depend, in particular, on the substrate type and on the complex dependence of the concentration of structural imperfections on the used technology and growth conditions of the structures. 相似文献
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<正>A method to drastically reduce dislocation density in a GaN film grown on an Si(111) substrate is newly developed. In this method,the Si_xN_y interlayer which is deposited on an A1N buffer layer in situ is introduced to grow the GaN film laterally.The crack-free GaN film with thickness over 1.7 micron is successfully grown on an Si(111) substrate. A synthesized GaN epilayer is characterized by X-ray diffraction(XRD),atomic force microscope(AFM),and Raman spectrum.The test results show that the GaN crystal reveals a wurtzite structure with the(0001) crystal orientation and the full width at half maximum of the X-ray diffraction curve in the(0002) plane is as low as 403 arcsec for the GaN film grown on the Si substrate with an Si_xN_y interlayer.In addition,Raman scattering is used to study the stress in the sample.The results indicate that the Si_xN_y interlayer can more effectively accommodate the strain energy.So the dislocation density can be reduced drastically,and the crystal quality of GaN film can be greatly improved by introducing an Si_xN_y interlayer. 相似文献
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在Si(100)衬底上用分子束外延在不同的温度下生长了不同组份的GexSi1-x/Si应变层超晶格。用反射式高能电子衍射、X射线双晶衍射、卢瑟福背散射、透射电子显微镜以及Raman。散射等测试方法研究了GexSi1-x/Si超晶格的生长及其结构特性。结果表明,对不同合金组份的超晶格,其最佳生长温度不同。x值小,生长温度高;反之,则要求生长温度低。对于x为0.1—0.6,在400—600℃的生长温度范围能够长成界面平整、
关键词: 相似文献
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Günther M. Prinz Martin Feneberg Martin Schirra Rolf Sauer Klaus Thonke Sarad B. Thapa Ferdinand Scholz 《固体物理学:研究快报》2008,2(5):215-217
Si‐doped aluminum nitride layers show a shift of the near‐band‐edge luminescence at around 6 eV to lower energies for increasing Si concentration up to ≈(1–3) × 1019 cm–3. For higher concentrations, the luminescence shifts back to higher energies. This behavior is compared to concomitant shifts of the Raman‐active E2 vibrational mode and to X‐ray diffraction data. It can be explained in terms of increasing tensile strain which finally relaxes due to the formation of cracks. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Y. A. Pusep A. D. Rodrigues L. J. Borrero‐Gonzlez L. N. Acquaroli R. Urteaga R. D. Arce R. R. Koropecki M. Tirado D. Comedi 《Journal of Raman spectroscopy : JRS》2011,42(6):1405-1407
Unexpectedly, the Fano resonance caused by the interference of continuum electron excitations with the longitudinal optical (LO) phonons was observed in random porous Si by Raman scattering. The analysis of the experimental data shows that the electron states trapped at the Si SiO2 interface dominate in the observed Raman scattering. The gap energy associated with the interface states was determined. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Wataru Yashiro Kazushi Sumitani Toshio Takahashi Yoshitaka Yoda Kazushi Miki 《Surface science》2004,550(1-3):93-105
A new technique to observe mesoscopic-range strain fields (up to several hundreds of nm) is proposed, using modulation of the crystal-truncation-rod (CTR) scattering caused by Bragg reflection. This technique is particularly sensitive to small, long-range strain fields near crystal surfaces and interfaces, which are usually difficult to be discriminated by using Bragg reflection. A simple interpretation can be made for the modulation profile: the technique is physically simple with a few parameters fitted to the data and, independently of any model, is able to determine the total displacement due to mesoscopic strain field for depths up to several hundreds of nanometers. We applied this method to a Si(0 0 1) wafer whose surface is covered with a thermal oxide layer 3 nm thick. On the basis of the expressions we obtained for the modulation profile a least-squares fitting was carried out to give a result that under the oxide layer there exists a total displacement of −0.16 Å. It was also revealed from the visibility of the modulation profile that the total displacement has a static fluctuation of at least ±0.13 Å in the lateral direction. The new method can be used for the correction of the errors of the X-ray standing wave (XSW) method produced by strained layers near crystal surfaces. 相似文献
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采用脉冲激光烧蚀技术,在室温、低压Ar气条件下通过改变气体压强及靶与衬底间距,对纳米Si晶粒成核的气压阈值进行了研究.根据扫描电子显微镜图像、拉曼散射谱和X射线衍射谱对制备样品的表征结果,确定了在室温、激光能量密度为4 J/cm2、靶与衬底间距为3 cm条件下形成纳米Si晶粒的阈值气压为0.6 Pa.结合流体力学模型和成核分区模型,对纳米晶粒的成核动力学过程进行了分析.通过Monte Carlo数值模拟,表明在气相成核过程中,烧蚀Si原子的温度和过饱和密度共同影响着纳米晶粒的成核.
关键词:
脉冲激光烧蚀
成核
气压阈值
Monte Carlo数值模拟 相似文献
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A. Czyzak J.Z. Domagala G. Maciejewski Z.R. Zytkiewicz 《Applied Physics A: Materials Science & Processing》2008,91(4):601-607
Spatially resolved X-ray diffraction (SRXRD) is used for micro-imaging of strain in GaAs:Si layers grown by liquid phase epitaxial
lateral overgrowth (ELO) on SiO2-masked GaAs substrates. We show that laterally overgrown parts of the layers (wings) are tilted towards the underlying mask.
By SRXRD mapping local wing tilt is easily distinguished from macroscopic sample curvature. The direction of the tilt and
distribution of tilt magnitude across the width of each layer can also be readily determined. This allows measuring of the
shape of the lattice planes in individual ELO stripes. Downward wing tilt disappears completely when the mask is removed by
selective etching. Then residual strain in ELO layers is exposed. In particular, upward tilt is found in free-standing ELO
wings. Numerical simulations show that this phenomenon is caused by different concentrations of silicon dopant in vertically
and laterally grown parts of the layer.
PACS 61.05.cp; 61.72.Ff; 68.55.ag 相似文献
18.
A method to drastically reduce dislocation density in a GaN film grown on an Si(111) substrate is newly developed. In this method, the SixNy interlayer which is deposited on an AlN buffer layer in situ is introduced to grow the GaN film laterally. The crack-free GaN film with thickness over 1.7 micron is grown on an Si(111) substrate successfully. Synthesized GaN epilayer is characterized by X-ray diffraction (XRD), atomic force microscope (AFM), and Raman spectrum. The test results show that the GaN crystal reveals a wurtzite structure with the <0001> crystal orientation and the full width at half maximum of the X-ray diffraction curve in the (0002) plane is as low as 403 arcsec for the GaN film grown on the Si substrate with an SixNy interlayer. In addition, Raman scattering is used to study the stress in the sample. The results indicate that the SixNy interlayer can more effectively accommodate the strain energy. So the dislocation density can be reduced drastically, and the crystal quality of GaN film can be greatly improved by introducing SixNy interlayer. 相似文献
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The solid solution of 0.1BiFeO3-0.9Bi4Ti3O12 (BF-BT) with bismuth-layered perovskite structure was obtained by conventional solid-state reaction. The lattice instability of BF-BT has been investigated by variable-temperature Raman scattering and X-ray diffraction. The results showed that there was a ferroelectric phase transition in the 450∼550 °C region in terms of the evolution of temperature dependence of Raman scattering frequencies. Some changes at about 530 °C in the XRD lines, the lattice parameters (a, b and c) as well as the orthorhombic distortion b/a have been detected in the high temperature X-ray diffraction, which can be interpreted by a phase transition and it is in good agreement with the results of high temperature Raman scattering. PACS 77.80.Bh; 61.10.Eq; 63.20.Dj 相似文献
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The authors report the growth of crack-free GaN on Si(1 1 1) substrate with step-graded AlGaN intermediate layers all grown at 1120 °C. By preparing all these layers at high-temperature, we can simplify the growth proceduce and minimize the growth time. Using X-ray diffraction and transmission electron microscopy, it was found that the high-temperature step-graded AlGaN intermediate layers can effectively reduce the tensile stress on GaN epitaxial layers. Photoluminescence and Raman measurements also indicate that we can improve the crystal quality of GaN by inserting the step-graded AlGaN intermediate layers. 相似文献