分子束外延ZnSe/GaAs材料的拉曼散射研究

用分子束外延(MBE)技术，在GaAa(100)衬底上生长了厚度从0．045μm到1．4μm的ZnSe薄膜。通过室温拉曼光谱的测量对ZnSe薄膜纵光学声子(Longitudinal-opticalphonon)的谱形进行了分析。用拉曼散射的空间相关模型定量分析了一级拉曼散射的型间相关长度与晶体质量之间的关系，结果表明ZnSe外延层的晶体质量随着外延层厚度的减薄是渐渐退化的，这是由于界面失配位错引入外延层所致，理论分析与实验结果相吻合。     

压电晶体拉曼散射的统一量子论

发展了拉曼散射的一个广义量子理论，它能同时说明非极性模和极性模的作用.在场论中， 光被纵光学和横光学模的拉曼散射能在一个统一的理论框架内描述. 关键词： 拉曼散射 声子 量子场论     

LPE碲镉汞薄膜的显微Raman谱与显微荧光谱分析

利用Raman显微镜系统对4块用液相外延(LPE)方法在Cd0.96Zn0.04Te衬底上生长的Hg0.8Cd0.2Te外延薄膜样品，在100～5 000cm^-1光谱范围进行测量，在实验曲线中除了观察到与碲镉汞材料晶格振动相符的类．HgTe的光学振动横模(TO1模)和纵模(LO1模)的Raman散射峰、类-CdTe光学振动横模(TO2模)和纵模(LO2模)混合的Raman散射峰以及来源于TO1 LO1的二级Raman散射峰外，在1 000～5 000cm^-1光谱范围首次发现了LPE碲镉汞薄膜的显微荧光峰，该显微荧光的发光范围换算为电子伏特标度为1．34～1．83eV．发光中心位于2750cm^-1即1.62eV，发光峰的半高宽(FWFIM)约为0．25eV。通过分析指出．该显微荧光来源于碲镉汞外延层中阴性离子空位与材料导带底的共振能级的发光。     

n-SiC的电子拉曼散射及二级拉曼谱研究

研究了利用离子注入法得到的掺氮n-SiC拉曼光谱. 理论线形分析表明,与4H-SiC相比,6H-SiC中LO声子等离子体激元耦合模(LOPC模)拉曼位移随自由载流子浓度变化较小. 5145nm激发光下得到的电子拉曼散射光谱表明,k位处由1s(A₁)到1s(E)的能谷轨道跃迁带来的拉曼谱6H-SiC中有四条,4H-SiC中有二条;高频6303及635cm^-1处观察到的谱线被认为与深能级缺陷有关. 最后,利用纤锌矿型结构二级拉曼散射选择定则指认了6 关键词： 碳化硅 电子拉曼散射 轨道能谷分裂 倍频谱     

Al和Sb共掺对ZnO有序阵列薄膜的结构和光学性能的影响

采用水热合成法在预先生长的ZnO种子层的玻璃衬底上制备出Al和Sb共掺ZnO纳米棒有序阵列薄膜. 通过X射线衍射、扫描电镜、透射电镜和选区电子衍射分析表明:所制备的薄膜由垂直于ZnO种子层的纳米棒组成, 呈单晶六角纤锌矿ZnO结构, 且沿[001]方向择优生长, 纳米棒的平均直径和长度分别为27.8 nm和1.02 μm. Al和Sb共掺ZnO纳米棒有序阵列薄膜的拉曼散射分析表明:相对于未掺杂ZnO薄膜的拉曼振动峰(580 cm^-1), Al和Sb共掺ZnO阵列薄膜的E₁(LO)振动模式存在拉曼位移. 当Al和Sb的掺杂量为3.0at%,4.0at%,5.0at%,6.0at%时, Al和Sb共掺ZnO阵列薄膜的拉曼振动峰的位移量分别为3,10,14,12 cm^-1. E₁ (LO) 振动模式位移是由Al和Sb掺杂ZnO产生的缺陷引起的. 室温光致发光结果表明:掺杂Al和Sb后, ZnO薄膜在545 nm处的发光强度减小,在414 nm处的发光强度增加. 这是由于掺杂Al和Sb后, ZnO薄膜中Zn_i缺陷增加, O_i缺陷减少引起的. 关键词： Al和Sb共掺ZnO薄膜 纳米棒有序阵列 结构表征 拉曼散射     

n-SiC拉曼散射光谱的温度特性

测量了采用离子注入法得到掺N的n-SiC晶体从100—450 K的拉曼光谱. 研究了SiC一级拉曼谱、电子拉曼散射谱及二级拉曼谱的温度效应. 实验结果表明,大部分SiC一级拉曼峰会随温度升高向低波数方向移动,但声学模红移(峰值位置向低频方向移动)的幅度较光学模小. 重掺杂4H-SiC的纵光学声子等离子体激元耦合(LOPC)模频率随温度升高表现出先蓝移(峰值位置向高频方向移动)后红移的变化趋势,表明LOPC模的温度特性不仅会受到非简谐效应的影响,还与实际已离化杂质浓度有关. 电子拉曼散射峰线宽随温度升高而增 关键词： 碳化硅 温度 纵光学声子等离子体激元耦合模 电子拉曼散射     

InGaN合金中LO声子-等离子激元耦合模的研究

分别采用532,488 nm可见光和325 nm紫外光激发,对金属有机化学气相沉积法在蓝宝石衬底上生长的六方相InGaN/GaN薄膜样品在室温和78 K低温下的拉曼散射谱进行了研究。在可见光激发时,E₂模和A₁(LO)模的散射信号主要来自GaN层;采用紫外光激发时,A₁(LO)模向低频方向移动且共振增强,此散射信号来自InGaN层。在可见光激发的情况下,在A₁(LO)模的高频方向观察到一个宽峰,此宽峰为InGaN的LO声子-等离子激元耦合模,根据耦合模频率得到InGaN层中的电子浓度为n_ｅ＝1.61×1018 cm-3。紫外光激发时,没有观察到耦合模,A₁(LO)模散射信号主要来自样品表面耗尽层,由此估算样品中的耗尽层宽度大约在40 nm。此外,还对比分析了在室温和78 K低温下LO声子-等离子激元耦合模的散射强度的变化规律,计算了不同温度下等离子激元的屏蔽波矢。这些结论对于了解InGaN材料的基本性质以及氮化物光电器件的开发利用都有重要参考价值。     

分子束外延GaAs/Si材料的喇曼散射研究

对逐层腐蚀的GaAs/Si材料进行喇曼散射实验,研究晶格振动声子谱沿外延生长方向的剖面分布,发现GaAs外延层从表面到界面经历着从双轴张应力到双轴压应力的变化。用Anastassakis等人提出的特殊相关模型对GaAsLO声子的谱形进行分析,发现GaAs外延层的晶体质量随着外延层厚度的减薄(从1μm—500?)是渐渐退化的,这是由于界面失配位错进入外延层所致。对GaAs LO声子与TO声子强度之比分析表明:外延层厚度从3.3μm变化到1μm左右时,其晶体质量并不是简单地随着厚度的减薄而退化,在1.3μm左右外延层晶体质量反而变好。对这种现象做了详细的讨论。 关键词：     

静压下(CdTe)_2(ZnTe)_4-ZnTe多量子阱结构的多声子共振拉曼散射

用加静高压的方法改变光学能隙来实现共振条件。在以(CdTe)_2(ZnTe)_4短周期超晶格为阱层,(ZnTe)_(4)为垒层的多量子阱结构中观察到高达四阶的类 ZnTe 纵光学声子模的多声子共振拉曼散射。通过对拉曼位移随压力变化的分析,发现在与(CdTe)_2(ZnTe)_4短周期超晶格共振时测得的类ZnTe 纵光学声子模的频率比与 ZnTe 势垒层共振时测得的 ZnTe 纵光学声子模的频率低4cm~(-1)。并将它归结为在短周期超品格中纵光学声子模的限制效应。在与短周期超品格严格的2LO 声子出射共振条件下观察到了类 CdTe 的2LO 声子的共振拉曼峰。     

六方相InGaN外延膜的显微Raman散射

用X射线衍射(XRD)技术和显微Raman散射方法对金属有机化学气相沉积(MOCVD)法生长的六方相In_xGa_1-xN薄膜样品进行了研究，观察到了相分离现象和LO声子-等离子耦合模(LPP⁺)，讨论了In_xGa_1-xN的A₁(LO)模被屏蔽的主要物理机制.同时，对Raman谱中E₂和A₁(TO)声子模进行了分析和讨论.在In_xGa_1-xN样品的低温Raman谱中还观察到单电子跃迁产生的Raman散射信号. 关键词： Raman散射 X射线衍射 相分离 应力 LO声子-等离子耦合     

Structural modifications of GaN after cerium implantation

Among the family of rare earth (RE) dopants, the doping of first member Ce into GaN is the least studied system. This article reports structure properties of Ce‐doped GaN realized by technique of ion implantation. Ce ions were implanted into metal organic chemical vapor deposition grown n‐ and p‐GaN/sapphire thin films at doses 3 × 10¹⁴ and 2 × 10¹⁵ cm⁻². X‐ray diffraction scans and Raman scattering measurements exhibited expansion of lattice in the implanted portion of the samples. First order Raman scattering spectra show appearance of several disorder‐activated Raman scattering modes in addition to typical GaN features. A dose‐dependent decrease in intensity of E₂ mode was observed in Raman the spectra of the implanted samples. Ultraviolet Raman spectra of implanted samples show complete quenching of photoluminescence emission and appearance of multiple A₁(LO) phonon scattering modes up to fifth order. Moreover, a decrease in intensity and an increase in line width of LO modes as a function of wavenumber were observed for implanted samples. Copyright © 2012 John Wiley & Sons, Ltd.     

Surface polariton dispersion measurement by Raman scattering excited in total reflection condition

We report the first measurement of phonon surface polariton (s.p.) dispersion by a non-forward Raman scattering geometry. The Raman scattering from surface modes was excited by the evanescent electromagnetic wave produced by total reflection at the interface between two transparent media. This Raman Scattering excited in condition of Total Reflection, RSTR, has been applied to the NaClO₃-sapphire interface for studying the surface polariton dispersion in the gap between the TO frequency at 966 cm^-1 and the LO frequency at 983 cm^-1 of sodium chlorate. Comparison is made between the experimental and theoretical dispersion curves.     

Morphology of InN nanorods using spectroscopic Raman imaging

We report the vibrational properties of vertical and oblique InN nanorods (NRs) grown by molecular beam epitaxy (MBE). Surface optical (SO) Raman mode at 561 cm⁻¹, belonging to E₁ symmetry [SO(E₁)], is identified along with symmetry allowed Raman modes of E₂(low), E₂(high), and E₁(LO) at 87, 489, and 589 cm⁻¹, respectively, corresponding to wurtzite InN phase. Usually, SO phonon modes arise due to breakdown of translational symmetry of surface potential at surface defects, which are attributed by the surface roughness. Intensity distribution of E₁(LO) and SO(E₁) phonon modes over a specified area have been analysed using Raman area mapping with an optical resolution of 400 nm. Imaging with E₁(LO) phonon mode, originating from the bulk of the sample, distinguishes the vertical NRs alone. We are able to resolve NR morphologies in both vertical and oblique cases with additional Raman mapping analysis of SO(E₁) phonon mode, emerging from the surface irregularities, which are confined to the tip of MBE grown NRs. Copyright © 2013 John Wiley & Sons, Ltd.     

Multiphonon resonant Raman scattering in N‐doped ZnO

Multiphonon resonant Raman scattering in N‐doped ZnO films was studied, and an enhancement of the resonant Raman scattering process as well as longitudinal optical (LO) phonon overtones up to the sixth order were observed at room temperature. The resonant Raman scattering intensity of the 1LO phonon in N‐doped ZnO appears three times as strong as that of undoped ZnO, which mainly arises from the defect‐induced Raman scattering caused by N‐doping. The nature of the 1LO phonon at 578 cm⁻¹ is interpreted as a quasimode with mixed A₁ and E₁ symmetry because of the defects formed in the ZnO lattice. In addition, the previously neglected impurity‐induced two‐LO‐phonon scattering process was clearly observed in N‐doped ZnO. Copyright © 2009 John Wiley & Sons, Ltd.     

气相外延GaN的拉曼散射

测量了在蓝宝石衬底上气相外延生长GaN的拉曼散射谱.除观察到已被确认的两个E2,一个A1(TO)和一个E1(TO)声于振动以外,在734±3cm-1处观察到一个散射峰且从实验上确认其为GaN的纵向光学声子模E1(LO).而且发现其强度与外延层晶体质量密切相关.A1(TO)和高频E2散射峰相对强度变化显示不同生长条件引起的外延层质量的变化.     

Phonon freedom and confinement in GaAsAlxGa1−xAs superlattices

Phonon modes in GaAsAl_xGa_1?xAs superlattices simplify when the phonon wavevector q is perpendicular to the plane of the layers. We have studied such modes using a Raman back-scattering technique on SL's grown by MBE. The results are consistent with simple ideas of LA phonon freedom and LO phonon confinement suggested by one-dimensional lattice dynamical calculations. The longitudinal acoustic (LA) modes show zone folding due to mini-zone formation. Their frequencies occur in doublets linearly dependent on q and show little mini-gap formation. This is consistent with a picture of approximately free plane wave propagating through the interfaces with Raman coupling due to SL layering of the photoelastic coefficient. By contrast, Raman data on LO modes in small period GaAsAlAs SL's suggest that these modes are standing waves strongly confined in either GaAs or AlAs.     

Raman scattering for lead telluride-based thin film structures

For single-crystal epitaxial lead telluride films, Raman spectra obtained under conditions in which the intensity of incident radiation is minimized in order to suppress photo-initiated oxidative process are presented. The spectra were measured with an InVia Renishaw spectrometer at an exciting radiation wavelength of 514.5 nm and in-line focusing of a 20-μW beam. These measuring conditions allowed us for the first time to experimentally observe a large set of peaks for lead telluride, the positions of which were in line with the theoretical values of harmonics and combinatorial PbTe phonon modes. In order to demonstrate the possibilities of the methodology used, the picture of phonon modes for single-crystal and polycrystalline films of the Pb_{1 ? x} Eu _x Te (0.05 ? x ? 0.10) solution was additionally considered.     

Raman studies of lattice and local vibrational modes of GaInNAs prepared by molecular beam epitaxy

Polarized Raman spectra have been studied on the lattice-matched Ga_0.94In_0.06N_0.025As_0.975 epitaxial layers grown on (100) GaAs by molecular beam epitaxy. Polarization dependence of TO and LO phonon modes has been examined. The N-related local vibrational mode (LVM) in GaInNAs has been studied with emphasis on the light polarization and the effect of the thermal annealing. The thermal annealing-induced change of the N-related LVM in GaInNAs is discussed in terms of the local atomic arrangement around N atoms.     

Normal incidence Raman scattering enhancement in double-cavity microresonators

We report on the observation of huge enhancements of the Raman scattering efficiency at quasi-backscattering due to double optical resonances in a microcavity. The structure, based on a double-cavity configuration separated by a central mirror, was specifically designed and grown by molecular beam epitaxy to achieve a large splitting, close to the energy of the LO phonon of GaAs, between the two confined photon modes.