共查询到20条相似文献，搜索用时 93 毫秒
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Influence of electron‐beam (e‐beam) irradiation on multi‐walled (MW) and single‐walled (SW) carbon nanotube films grown by microwave chemical vapor deposition technique is investigated. These films were subjected to an e‐beam energy of 50 keV from a scanning electron microscope for 2.5, 5.5, 8.0, and 15 h, and to 100 and 200 keV from a transmission electron microscope for a few minutes to ∼2 h continuously. Such conditions resemble an increased temperature and pressure regime enabling a degree of structural fluidity. To assess structural modifications, they were analyzed prior to and after irradiation using resonance Raman spectroscopy (RRS) in addition to in situ monitoring by electron microscopy. The experiments showed that with extended exposures, both types of nanotubes displayed various local structural instabilities including pinching, graphitization/amorphization, and formation of an intramolecular junction (IMJ) within the area of electron beam focus possibly through amorphous carbon aggregates. RRS revealed that irradiation generated defects in the lattice as quantified through (1) variation of the intensity of radial breathing mode (RBM), (2) intensity ratio of D to G band (ID/IG), and (3) positions of the D and G bands and their harmonics (D* and G*) and combination bands (D + G). The increase in the defect‐induced D band intensity, quenching of RBM intensity, and only a slight increase in G band intensity are some of the implications. The MW nanotubes tend to reach a state of saturation for prolonged exposures, while the SW ones transform from a semiconducting to a quasi‐metallic character. Softening of the q = 0 selection rule is suggested as a possible reason to explain these results. Furthermore, these studies provide a contrasting comparison between MW and SW nanotubes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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In this paper, we report on the diameter distribution of boron‐doped single‐walled carbon nanotubes grown from triethyl borate with high vacuum chemical vapor deposition, using multi‐frequency Raman resonance spectroscopy. The nanotube yield is higher than in previously reported material produced with the same method. Our results suggest that the amount of as‐grown material and the range of diameters are directly correlated with feedstock used in the synthesis. The ID/IG ratio shows that the morphology of the samples is critically affected by the temperature. The population of diameters in the optimal conditions shows a Poisson distribution with a mean value at ∼1.15 nm. 相似文献
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Marianna V. Kharlamova Christian Kramberger Thomas Pichler 《physica status solidi b》2016,253(12):2433-2439
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对不同激发波长下单壁和多壁碳纳米管的激光拉曼光谱进行了比较。发现单壁碳纳米管D峰强度和G峰强度的比值(ID/IG)几乎不随激发光子能量的改变而变化,多壁碳纳米管ID/IG值随着激发光子能量的增加以斜率0 3/eV减小。并对此现象进行了初步的分析。此外,还发现在1064nm激发波长下,单壁和多壁碳纳米管2500-3500cm-1之间拉曼峰的相对强度随着入射激光功率的增加而增加。 相似文献
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Mihaela Baibarac Ioan Baltog Adelina Matea Lucian Mihut Serge Lefrant 《Journal of Raman spectroscopy : JRS》2015,46(1):32-38
Although Raman spectra reveal, as a signature of double‐walled carbon nanotubes (DWCNTs), two radial breathing mode (RBM) lines associated with the inner and outer tubes, the specification of their nature as metallic or semiconducting remains a topic for debate. Investigating the spectral range of the RBM lines, we present a new procedure of the indexing of the semiconducting or metallic nature of the inner and outer shell that forms the DWCNT. The procedure exploits the difference between the intensities of recorded anti‐Stokes Raman spectrum and the anti‐Stokes spectrum calculated by applying the Boltzmann formulae to the recorded Stokes spectrum. The results indicate that the two spectra do not coincide with what should happen in a normal Raman process, namely, that there are RBM lines of the same intensity in both spectra, as well as RBM lines of higher intensity that are observed in the calculated spectrum. This discrepancy results from the surface‐enhanced Raman scattering mechanism that operates differently on metallic or semiconducting nanotubes. In this context, the analysis of the RBM spectrum can reveal pairs of lines associated with the inner/outer shell structure of DWCNT, and when the intensities between the recorded and calculated spectra coincide, the nanotube is metallic; otherwise, the nanotube is semiconducting. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Jen&#x; Kürti Jnos Koltai Blint Gyimesi Hans Kuzmany 《physica status solidi b》2015,252(11):2541-2545
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介绍了一种碳纳米管表面增强散射的新方法。该方法消除了溶剂的干扰,保证了结果的准确性,理论分析和实验结果证明该方法是正确的,可行的。 相似文献
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Mingguang Yao Shuangchen Lu Junping Xiao Zhen Yao Linhai Jiang Tian Cui Bingbing Liu 《physica status solidi b》2013,250(7):1370-1375
Raman spectra of single‐walled carbon nanotubes (SWNTs) with diameter distribution of 0.6–1.6 nm have been studied under high pressure. We focused on the dependence of radial R‐band frequency (associated with the radial breathing mode, RBM) on pressure, dωRBM/dP, and studied the effect of experimental factors on the structural changes of nanotubes under pressure. We found that the nanotube diameter and the pressure transmission medium (PTM) strongly affect the dωRBM/dP dependence of a nanotube in the experiments with PTMs, while the nanotube diameter and the intertube interactions between the tube walls play a dominant role on the upshift of RBMs for nanotubes without a PTM. These results are in line with the theoretical predictions that PTMs have a strong effect on the pressure‐induced shift in the R‐bands of SWNTs. In addition, we found that the collapse of nanotubes and their reversibility depend not only on diameter and pressure environment but also on the sample quality. This could explain that there have been different results reported by different groups even for nanotubes with the same diameter distribution. 相似文献
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G. Ruiz‐Soria P. Ayala S. Puchegger H. Kataura K. Yanagi T. Pichler 《physica status solidi b》2011,248(11):2504-2507
In this paper, we report a facile purification method of boron‐doped single‐walled carbon nanotubes (SWCNTs) produced by high vacuum chemical vapor deposition (HV‐CVD). The raw material was doped in situ during growth, with a B content below 0.5 at.%, estimated by means of X‐ray photoelectron spectroscopy (XPS). Using ultracentrifugation combined with a mild acid solution pH neutralization, we have proved it is feasible to purify this material, which originally contains synthesis byproducts that differ from the typical catalytic remaining in pristine carbon nanotube samples produced with a similar method. The diameter size and distribution – previous and after purification – have been monitored by multi‐frequency Raman spectroscopy. 相似文献
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Xianjie Liu Hans Kuzmany Takeshi Saito Thomas Pichler 《physica status solidi b》2011,248(11):2492-2495
The growth of inner tubes from ferrocene‐filled single‐walled carbon nanotubes was studied with Raman spectroscopy. Special attention was paid to inner tubes formation based on the annealing temperature and the outer tube diameter. Besides the presence of inner tubes radial breathing mode, a new Raman feature appears around 1250 cm−1, which is always related to the appearance of the inner tube. The thermal stability of the inner tube strongly depends on the outer tube diameter. The inner tube formed inside outer tube with 1 nm diameter is destructed at 1000 °C, but it can survive more than 1300 °C with outer tube diameter of about 1.6 nm. Furthermore, the splitting of G line and the shift of 2D line were discussed regarding to the appearance of inner tubes. 相似文献
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U. Dettlaff‐Weglikowska G. Kim L. G. Bulusheva S. Roth 《physica status solidi b》2011,248(11):2458-2461
We investigated the interactions of two aromatic amines, N,N,N′N′‐tetramethyl‐p‐phenylenediamine (TMPD) and tetramethylpyrazine (TMP) with single‐walled carbon nanotube (SWNT) networks. Adsorption and intercalation of amine molecules in bundled SWNTs is expected to modify the electronic structure of nanotubes in a similar way as has already been observed for alkali metals. Our ab initio density functional calculations demonstrate that TMPD donates electron to the nanotube and produces donor‐like states below the conduction band whereas the effect of the TMP treatment is very weak. The electron transfer to the nanotubes has been supported experimentally by the XPS valence band spectra which show strongly modified spectral features. Especially an increase of the electronic density at the Fermi level upon adsorption of TMPD and TMP is clearly demonstrated. Rather intensive features between π* and σ* transitions in the NEXAFS spectrum of the pristine SWNTs attributed to the oxidized carbon functional groups are chemically modified upon adsorption of amines on the networks. This fact suggests that the aromatic amines evidently react with the defects, remove or replace oxygen species responsible for the p‐type doping of SWNTs, and therefore are acting as a de‐doping agent for the naturally p‐type doped semiconducting SWNTs. 相似文献
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OUYANGY WANGY.P FANGY 《光散射学报》2005,17(1):71-73
介绍了一种单壁碳纳米管表面增强拉曼散射的新方法。依据碳纳米管独特的力学性能,在银表面直接研磨单壁碳纳米管,在形成纳米级粗糙银表面的同时,单壁碳纳米管也吸附在银表面上。在银表面粗糙程度和单壁碳纳米管厚度适中的区域得到了高质量的单壁碳纳米管SERS谱。该方法消除了溶剂的干扰,保证了结果的准确性,理论分析和实验结果表明该方法是正确的、可行的 相似文献