Nanoscale Characterization of Individual Horizontally Aligned Single-Walled Carbon Nanotubes (original) (raw)
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Near-field imaging and spectroscopy of electronic states in single-walled carbon nanotubes
Physica Status Solidi B-basic Solid State Physics, 2006
Near-field photoluminescence spectroscopy was used to study the electronic properties of semiconducting Single-Walled Carbon Nanotubes in different environments. A sharp laser-illuminated metal tip was raster scanned over the sample and served as a strongly confined excitation source. We observed localization of photoluminescence and variations of emission energies along nanotubes on a length scale of about 30 nm.
physica status solidi (b), 2016
We demonstrate that scattering-type near-field optical microscopy (s-SNOM) at infrared frequencies can be effectively used to distinguish between carbon nanotube (CNT) bundles based on their electrical properties. Samples from separated metallic and semiconductor nanotubes and their mixtures were investigated using infrared lasers under near-field conditions. In this frequency range, the difference in the free-carrier concentration between metallic and semiconducting tubes is expected to influence the properties of the scattered light. The remarkable difference in the optical phase images proves that this is indeed the case: the metallic and semiconducting bundles are unambiguously identifiable in the sample, even in case of 5 nm diameter bundles. The measurements agree qualitatively with our calculations based on the extended finite dipole model using the known optical functions of the constituting nanotubes.
Nanoscale Research Letters, 2012
During the recent years, a significant amount of research has been performed on single-walled carbon nanotubes (SWCNTs) as a channel material in thin-film transistors (Pham et al. IEEE Trans Nanotechnol 11:44-50, 2012). This has prompted the application of advanced characterization techniques based on combined atomic force microscopy (AFM) and Raman spectroscopy studies (Mureau et al. Electrophoresis 29:2266-2271. In this context, we use confocal Raman microscopy and current sensing atomic force microscopy (CS-AFM) to study phonons and the electronic transport in semiconducting SWCNTs, which were aligned between palladium electrodes using dielectrophoresis (Kuzyk Electrophoresis 32:2307-2313, 2011). Raman imaging was performed in the region around the electrodes on the suspended CNTs using several laser excitation wavelengths. Analysis of the G + /G − splitting in the Raman spectra (Sgobba and Guldi Chem Soc Rev 38:165-184, 2009) shows CNT diameters of 2.5 ± 0.3 nm. Neither surface modification nor increase in defect density or stress at the CNT-electrode contact could be detected, but rather a shift in G + and G − peak positions in regions with high CNT density between the electrodes. Simultaneous topographical and electrical characterization of the CNT transistor by CS-AFM confirms the presence of CNT bundles having a stable electrical contact with the transistor electrodes. For a similar load force, reproducible current-voltage (I/V) curves for the same CNT regions verify the stability of the electrical contact between the nanotube and the electrodes as well as the nanotube and the AFM tip over different experimental sessions using different AFM tips. Strong variations observed in the I/V response at different regions of the CNT transistor are discussed.
The Journal of Physical Chemistry Letters, 2010
The diameter of single-walled carbon nanotubes (SWNTs) is an important characteristic to determine their electronic properties and direct further applications in electronics and photonics. A demand currently exists for an accurate and rapid method of evaluating the mean diameter and diameter distribution of bulk SWNTs. Here, we provide an effective means for quantifying the diameter distribution of SWNTs using optical absorption spectroscopy without a strict prior assumption on the form of the diameter distribution. Verification of this assignment protocol is based upon statistical analysis of hundreds of highresolution transmission electron microscopy (HRTEM) images as well as comparison with Raman measurements on the same SWNT samples. A good agreement among different techniques indicates that this approach enables accurate and rapid assessment of diameter distribution and can be extended to bulk SWNT samples with various diameter distributions.
Efficient Spectrofluorimetric Analysis of Single-Walled Carbon Nanotube Samples
Analytical Chemistry, 2011
S ingle-walled carbon nanotubes (SWCNTs) constitute a family of novel nanomaterials of great interest for their unusual physical properties and potential applications. All SWCNTs are ordered tubular arrays of carbon atoms covalently linked by sp 2 bonds. However, they may differ in diameter (d t ), roll-up angle (θ), and length (l). The electronic properties of high aspect ratio SWCNTs are independent of length but vary strongly with diameter and roll-up angle. These two parameters are uniquely defined by a pair of integers (n,m) that index all possible SWCNT structures by reference to a graphene sheet. SWCNTs in which nÀm is evenly divisible by 3 are metallic or semimetallic, whereas others are semiconducting. 1 Moreover, the semiconducting band gaps are nearly proportional to inverse diameter and also depend on roll-up angle. A semiconducting SWCNT with diameter near 1 nm has band gap absorption and emission (E 11 ) in the near-IR (NIR). Each such semiconducting nanotube also has visible and near-UV optical transitions (E 22 , E 33 , etc.; see , Supporting Information).
Complex Optical Study of Carbon Nanotubes with a Narrow Diameter Distribution
Journal of Nanoelectronics and Optoelectronics, 2013
This work is dedicated to the complex optical diagnostics of carbon nanotube samples with a narrow diameter distribution. Nanotubes were synthesized with a modified CVD growth technique, which provides the samples of single-wall carbon nanotubes with only few close diameters. We have used three optical methods (UV-vis-NIR optical absorption spectroscopy, Raman spectroscopy and photoluminescence) to make the overall characterization of the samples. A new technique has been proposed providing the measurement of electronic parameters of the nanotubes with the resonant Raman scattering only. Under the different excitation energies the different bands in the Raman spectra (breathing modes, one-or two-phonon scattering) could dominate due to "outcoming" resonances occurring in case of an exact coincidence of the scattered photon energy with the electronic transition. The estimation of electronic transition values was based on the difference of the incoming light energy and the energy of vibration dominating in spectrum under this excitation. The Raman estimations have been confirmed by direct data of UV-vis-NIR optical absorption and photoluminescence spectroscopy.
Single Carbon Nanotube Optical Spectroscopy
Chemphyschem, 2005
. Temporal evolution of the SWNT fluorescence spectrum at T = 1.8 K. The right panel represents specific spectra extracted from the left panel, clearly showing evidence of spectral diffusion and intensity blinking.
Nano Letters, 2002
We report a method to investigate the same individual single-walled carbon nanotube (SWNT) bundles with both transmission electron microscopy (TEM) and Raman spectroscopy. Free-standing individual bundles are obtained by depositing a solution of suspend SWNTs on a carbon film with a regular pattern of holes, which can be localized by TEM and also by confocal Raman microscopy. While most of the TEM images predict that the bundles consist of tubes with a similar diameter, we will show that occasionally a certain tube diameter can be associated with a particular radial breathing mode frequency of the Raman spectrum.
In-situ techniques in optical spectroscopy for the analysis of carbon nanotubes
2010
In-situ temperature studies of the Raman tangential (G-band) and D modes are reported here on singlewalled carbon nanotube engineered paper samples. The expansive temperature range was achieved through a temperature stage coupled with the Raman microprobe. The in-situ arrangement allowed for a large temperature variation while spectral data acquisitions were collected. Changes in the characteristics of the peaks were analyzed using a novel deconvolution and fitting algorithm featuring a pseudo-voigt function for the fitting. Results show the variation of spectral parameters over the temperature range and shows specifically the increase in D/G ratio with laser excitation is unaffected by temperature within the range.