纳米硅薄膜的Raman光谱

通过等离子增强化学气相沉积法,制备了本征和掺磷的氢化纳米硅薄膜(nc-Si:H)，研究了晶粒尺寸和掺杂浓度对纳米硅薄膜喇曼谱的影响。结果表明晶粒变小和掺杂浓度增加都使纳晶粒的TO模峰位逐渐偏离声子限制模型的计算值。X射线衍射和高分辨电镜像的结果表明晶粒变小导致硅晶粒应力增加，而掺要使晶粒内部杂质和缺陷增多，这些因素破坏了晶粒变小导致晶粒应力增加，而掺杂使晶粒内部杂质和缺陷增多，这些因素破坏了晶粒内晶格的平移对称性进一步减小声子的平均自由程，导致实验值偏离理论计算值。晶格平称对称性的破缺还体现在，随晶粒尺寸减小或掺杂浓度增加，喇曼谱中TA、L振动模的相对散射强度增加。

Raman谱研究不同缓冲层结构对Si_(1-x)Ge_x应力弛豫的影响

应用Raman散射谱研究超高真空化学气相淀积(UHV/CVD)生长的不同结构缓冲层对恒定组分上表层Si_(1-x)Ge_x层应力弛豫的影响。Raman散射的峰位不仅与Ge组分有关,而且与其中的应力状态有关。在完全应变和完全弛豫的情况下，Si_(1-x)Ge_x层中的Si-Si振动模式相对于衬底的偏移都与Ge组分成线性关系。根据实测的Raman峰位，估算了应力弛豫。结果表明

分子束外延低温生长GaAs的Raman光谱研究

对从GaAs衬底剥离下来的低温下分子束外延生长的GaAs(LTG-GaAs)薄膜进行了喇曼光谱测量，研究了不同温度下生长的LTG-GaAs在退火前后晶体完整性的变化。首次观测到了190℃生长样品中As沉淀物所引起的喇曼峰，并证明800℃快速热退火30秒后产生的As沉淀物是无定形As。

InAs/InP（0.7）Sb（0.3）热电子晶体管的fT及f（max）

于2010-11-23批量导入

ZnSe-ZnTe应变层超晶格的Raman光谱研究

于2010-11-23批量导入

Microstructure of the silicon film prepared near the phase transition regime from amorphous to nanocrystalline

A kind of hydrogenated diphasic silicon films has been prepared by a new regime of plasma enhanced chemical vapor deposition (PECVD) near the phase transition regime from amorphous to nanocrystalline. The microstructural properties of the films have been investigated by the micro-Raman and Fourier transformed Infrared (FT-IR) spectra and atom force microscopy (AFM). The obtained Raman spectra show not only the existence of nanoscaled crystallites, but also a notable improvement in the medium-range order of the diphasic films. For the FT-IR spectra of this kind of films, it notes that there is a blueshift in the Si-H stretching mode and a redshift in the Si-H wagging mode in respect to that of typical amorphous silicon film. We discussed the reasons responsible for these phenomena by means of the phase transition, which lead to the formation of a diatomic hydrogen complex, H-2* and their congeries.

Raman scattering and infrared absorption of silicon nanocrystals in silicon oxide matrix

Structural dependence on annealing of a-SiOx:H was studied by using infrared absorption and Raman scattering. The appearance of Raman peaks in the range of 513-519cm(-1) after 1170 degreesC annealing was interpreted as the formation nanocrystalline silicon with the sizes from 3-10nm. The Raman spectra also show the existence of amorphous-like silicon phase, which is associated with Si-Si bond re-construction at boundaries of silicon nanocrystallites. The presence of the shoulder at 980cm(-1) of Si-O-Si stretching vibration at 1085cm(-1) in infrared spectra imply that except that SiO2 phase, there is silicon sub-oxide phase in the films annealed at 1170 degreesC. This sub-oxide phase is located at the interface between Si crystallites and SiO2, and thus support the shell model for the mixed structures of Si grains and SiO2 matrix.

Observation of the resonant Raman behavior of individual single-walled carbon nanotubes

The different resonant Raman scattering process of single-walled carbon nanotubes (SWNTs) has been found between the Stokes and anti-Stokes sides of the radial breathing modes (RBMs), and this provides strong evidence that Raman spectra of some special diametric SWNTs are in resonance with their electronic transitions between the singularities in the one-dimensional electronic density of states in the valence and conduction bands, and other SWNTs axe beyond the resonant condition. Because of the coexistence of resonant and non-resonant Raman scattering processes for different diametric SWNTs, the relative intensity of each RBM does not reflect the proportion of a particular SWNT.

Effect of rapid thermal annealing on the Raman spectrum of Si0.33Ge0.67/Si (100) alloy

The effect of thermal annealing on the Raman spectrum of Si0.33Ge0.67 alloy grown on Si (100) by molecular beam epitaxy is investigated in the temperature range of 550-800 degrees C. For annealing below 700 degrees C, interdiffusion at the interface is negligible and the residual strain plays the dominant role in the Raman shift. The strain-shift coefficients for Si-Ge and Ge-Ge phonon modes are determined to be 915 +/- 215 cm(-1) and 732 +/- 117 cm(-1), respectively. For higher temperature annealing, interdiffusion is significant and strongly affects the Raman shift and the spectral shape.

Raman study on residual strains in thin 3C-SiC epitaxial layers grown on Si(001)

Raman scattering measurement has been used to study the residual strains in the thin 3C-SiC/Si(001) epilayers with a variation of film thickness from 0.1 to 1.2 mu m. which were prepared by chemical vapor deposition (CVD)growth. Two methods have been exploited to figure our the residual strains and the exact LO bands. The final analyzing results show that residual strains exist in the 3C-SiC epilayers. The average stress is 1.3010 GPa, and the relative change of the lattice constant is 1.36 parts per thousand. Our measurements also show that 3C-SiC phonons are detectable even for the samples with film thickness in the range of 0.1 to 0.2 mu m. (C) 2000 Published by Elsevier Science S.A. All rights reserved.

Electronic and vibrational Raman scattering in resonance with yellow luminescence transitions in GaN on sapphire substrate

We analyze low-temperature Raman and photoluminescence spectra of MBE-grown GaN layers on sapphire. Strong and sharp Raman peaks are observed in the low frequency region. These peaks, which are enhanced by excitation in resonance with yellow luminescence transitions, are attributed to electronic transitions related to shallow donor levels in hexagonal GaN. It is proposed that a low frequency Raman peak at 11.7 meV is caused by a pseudo-local vibration mode related to defects involved in yellow luminescence transitions. The dependence of the photoluminescence spectra on temperature gives additional information about the residual impurities in these GaN layers.