用显微拉曼扫描成象(mapping)法测集成电路中CoSi_2电极引起的应力

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用拉曼光谱研究多孔硅的光发射机制

用拉曼光谱研究多孔硅的光发射机制贾霖，王昕，张树霖（北京大学物理系北京１０００８０）李经建，陈泳，刘忠范，蔡生民（北京大学化学系北京１００８７１）沈电洪（中国科学院物理所北京１００８７１）ＴｈｅＳｔｕｄｙｏｆＴｈｅＬｉｇｈｔ－ｅｍｉｔｔｉｎｇＭｅｃｈ...     

激光拉曼数据采集系统的改进

激光拉曼数据采集系统的改进陈浩刘金全（北京大学物理系北京１００８７１）朱恪刘玉龙（中国科学院物理所北京１０００８０）ＡｂｓｔｒａｃｔＷｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｓｃｉｅｎｃｅａｎｄｔｅｃｈｎｏｌｏｇｙ，ｈｏｗｔｏｃｏｎｔｒｏｌｔｈｅｍａｃ...     

Zn_(1-x)Mn_xTe/ZnTe超晶格的多声子拉曼谱

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拉曼光谱在医学上的应用（Ⅱ）

拉曼光谱在医学上的应用（Ⅱ）余国滔（北京大学生命科学学院北京１００８７１）ＢｉｏｍｅｄｉｃａｌＡｐｐｌｉｃａｔｉｏｎｓｏｆＲａｍａｎＳｐｅｃｔｒｏｓｃｏｐｙ（Ⅱ）ＹｕｅＫｗｏｋｔｏ（ＣｏｌｅｇｅｏｆＬｉｆｅＳｃｉｅｎｃｅｓ，ＰｅｋｉｎｇＵｎｉｖｅｒｓ...     

关于半导体极薄层超晶格拉曼散射特征的研究

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BGO晶体的布里渊散射与弹性系数测量

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CdS／SiO_2半导体玻璃复合材料的低频Raman散射光谱研究

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突破分辨率极限的拉曼光谱学——简介近场光学与近场拉曼光谱

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碳纳米管的拉曼光谱及其温度效应

在室温下首次观察到碳纳米管的四级拉曼光谱，并且发现碳纳米管的Ｄ峰和Ｄ＊峰的斯托克斯线和反斯托克斯线频率不一致。此外，还发现碳纳米管的拉曼特征峰频率严重依赖样品的温度，随着温度增加，碳纳米管拉曼特征峰频率下移，频移与温度变化成线性关系。     

多脉冲激光对碳纳米管悬浮液光限幅特性影响

利用实验的方法研究了碳纳米管悬浮液对脉宽8 ns,波长532 nm多脉冲激光的光限幅效应.分析了直径分布为10~20 nm的多壁碳纳米管悬浮液对重复频率分别为1 Hz、 3 Hz、 5 Hz、 10 Hz情况下532 nm激光的光限幅效应,分析计算了不同重复频率下碳纳米管悬浮液的限幅阈值,比较了不同焦距的透镜会聚入射光束情况下对碳纳米管悬浮液光限幅效果的影响.实验结果表明：碳纳米管悬浮液对不同重复频率的532 nm 激光都具有较强的光限幅特性;碳纳米管悬浮液对激光在不同重复频率入射情况下的光限幅阈值变化很大,当入射激光的重复频率为5 Hz时,碳纳米管悬浮液的光限幅阈值比单脉冲激光入射时的限幅阈值低了2倍,重复频率为10 Hz时的限幅阈值比单脉冲时的限幅阈值低了近3倍;碳纳米管在紧焦系统中的光限幅效果更好.     

Stability of high-density one-dimensional excitons in carbon nanotubes under high laser excitation

Through ultrafast pump-probe spectroscopy with intense pump pulses and a wide continuum probe, we show that interband exciton peaks in single-walled carbon nanotubes (SWNTs) are extremely stable under high laser excitations. Estimates of the initial densities of excitons from the excitation conditions, combined with recent theoretical calculations of exciton Bohr radii for SWNTs, suggest that their positions do not change at all even near the Mott density. In addition, we found that the presence of lowest-subband excitons broadens all absorption peaks, including those in the second-subband range, which provides a consistent explanation for the complex spectral dependence of pump-probe signals reported for SWNTs.     

Static magneto-polarizability of cylindrical nanostructures

The static polarizability of cylindrical systems is shown to have a strong dependence on a uniform magnetic field applied parallel to the tube axis. This dependence is demonstrated by performing exact numerical diagonalizations of simple cylinders (rolled square lattices), armchair and zig-zag carbon nanotubes (rolled honeycomb lattices) for different electron-fillings. At low temperature, the polarizability as function of the magnetic field has a discontinuous character where plateau-like region are separated by sudden jumps or peaks. A one to one correspondence is pointed out between each discontinuity of the polarizability and the magnetic-field induced cross-over between the ground state and the first excited state. Our results suggest the possibility to use measurements of the static polarizability under magnetic field to get important informations about excited states of cylindrical systems such as carbon nanotubes. Received 29 March 2001 and Received in final form 8 August 2001     

Intrinsic and extrinsic effects in the temperature-dependent photoluminescence of semiconducting carbon nanotubes

The temperature dependence of the band gap of semiconducting carbon nanotubes was measured for ten different nanotube species. The unprecedented effectiveness in avoiding the effect of external strain, or any other effects originating from the surrounding environment, lead to an accurate measurement of the band gap temperature dependence, giving fundamental insight into the nanotube electron-phonon interaction. Small but reproducible energy shifts of the emission lines with temperature were observed, showing a moderate chirality dependence, well in agreement with recent theoretical calculations. In addition to the energy shift, a substantial narrowing of the emission lines was also observed. The removal of the temperature shift of the band gap allows the precise measurement of the effect of external strain on carbon nanotubes in different environments.     

低温下单壁碳纳米管拉曼光谱温度效应研究

在单壁碳纳米管的低温拉曼光谱测量过程中,发现径向呼吸模(RBM)和正切拉伸模(GM)的拉曼频移在低温下的温度效应和在高温时的温度效应存在着很大的区别,在低温下拉曼光谱的频移和温度并不呈线性关系。而且,在温度为210K时,单壁碳纳米管内部的振动结构可能发生了变化。在低温下单壁碳纳米管拉曼峰的强度的变化是不可逆的。     

Temperature dependence of the raman spectra of carbon nanotubes with 1064 nm excitation

In this report, the near infrared 1064 nm line of an Nd:YAG laser, which has strong thermal effect, was used as the excitation. A temperature dependence of the Raman spectra of carbon nanotubes was observed at different temperatures by varying the incident laser power. The results show that the relative Raman intensities to the tangential stretching mode (G mode) of the higher-order Raman modes within 2500–3500 cm⁻¹ increase with increasing excitation laser power at the sample and the changes in the relative Raman intensities are linear in the excitation laser power. This has not been reported elsewhere. Thorough analysis shows that this is a temperature dependence of double-phonon Raman scattering and maybe provide important information for the studying of CNTs and double-phonon Raman scattering.     

Amplification of terahertz radiation in carbon nanotubes

We investigate theoretically the feasibility of amplification of terahertz radiation in aligned achiral carbon nanotubes, a zigzag (12,0) and an armchair (10,10) in comparison with a superlattice using a combination of a constant direct current (dc) and a high-frequency alternate current (ac) electric fields. The electric current density expression is derived using the semiclassical Boltzmann transport equation with a constant relaxation time. The electric field is applied along the nanotube axis. Analysis of the current density versus electric field characteristics reveals a negative differential conductivity behavior at high frequency, as well as photon assisted peaks. The photon assisted peaks are about an order of magnitude higher in the carbon nanotubes compared to the superlattice. These strong phenomena in carbon nanotubes can be used to obtain domainless amplification of terahertz radiation at room temperature.     

One-dimensional character of combination modes in the resonance Raman scattering of carbon nanotubes

Resonance Raman spectroscopy with an energy tunable system is used to analyze the 600-1100 cm(-1) spectral region in single-wall carbon nanotubes. Sharp peaks are associated with the combination of zone folded optic and acoustic branches from 2D graphite. These combination modes exhibit a peculiar dependence on the excitation laser energy that is explained on the basis of a highly selective resonance process that considers phonons and electrons in low dimensional materials.     

催化裂解CH4制备碳纳米管的影响因素

以柠檬酸法制备的Fe MgO、Co MgO和Ni MgO为催化剂 ,CH4 为碳源气 ,H2 为还原气 ,在 873、973和 10 73K制备出碳纳米管 ,通过TEM和拉曼光谱表征 ,讨论了催化剂、制备温度、反应时间等因素对碳纳米管形貌、产率和内部结构的影响 .结果表明 :不同的催化剂在相同的温度下制备的碳纳米管的形态和内部结构有很大的差异 .其中Fe MgO催化剂制备的碳纳米管管径粗 ,且大小不均匀 ,而Ni MgO催化剂制备的碳纳米管管径较细、较均匀 .碳纳米管的产率随着裂解温度的变化而改变 .Fe MgO催化剂制备碳纳米管的产率随制备温度的升高而提高 ,而Ni MgO催化剂制备碳纳米管的产率随制备温度的升高而降低 .Fe MgO催化剂制备碳纳米管 ,在10 73K甚至更高的制备温度才能达到其最高产率 .Co MgO催化剂制备碳纳米管的产率在 973K左右产率较高 ,而用Ni MgO催化剂制备碳纳米管 ,则在 873K甚至更低的制备温度就能达到最高产率 .反应时间与碳纳米管的产率不成正比 ,有一最佳反应时间 ,如Ni MgO催化剂的最佳反应时间为 2h .