Direct observation of heat dissipation in individual suspended carbon nanotubes using a two-laser technique (original) (raw)
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Optical measurement of thermal transport in suspended carbon nanotubes
2008
Abstract Thermal transport in carbon nanotubes is explored using different laser powers to heat suspended single-walled carbon nanotubes��� 5 ��m in length. The temperature change along the length of a nanotube is determined from the temperature-induced shifts in the G band Raman frequency. The spatial temperature profile reveals the ratio of the contact thermal resistance to the intrinsic thermal resistance of the nanotube.
Spectroscopy Letters, 2014
We have examined the effect of high temperature on single-wall carbon nanotubes under air and nitrogen ambient by Raman spectroscopy. We observe the temperature dependence of the radial breathing mode and the G-band modes. The thermal expansion coefficient (b) of the bundled nanotubes is obtained experimentally using the estimated volume from Raman scattering. b behaves linearly with temperature from 0.33 Â 10 À5 K À1 to 0.28 Â 10 À5 K À1 in air and from 0.58 Â 10 À5 K À1 to 0.47 Â 10 À5 K À1 in nitrogen ambient, respectively. The temperature dependence of the radial breathing mode Raman frequencies is consistent with a pure temperature effect.
Thermal Conductance of an Individual Single-Wall Carbon Nanotube above Room Temperature
Nano Letters, 2006
The thermal properties of a suspended metallic single-wall carbon nanotube (SWNT) are extracted from its high-bias (I-V) electrical characteristics over the 300-800 K temperature range, achieved by Joule self-heating. The thermal conductance is approximately 2.4 nW/K and the thermal conductivity is nearly 3500 Wm -1 K -1 at room temperature for a SWNT of length 2.6 µm and diameter 1.7 nm. A subtle decrease in thermal conductivity steeper than 1/T is observed at the upper end of the temperature range, which is attributed to secondorder three-phonon scattering between two acoustic modes and one optical mode. We discuss sources of uncertainty and propose a simple analytical model for the SWNT thermal conductivity including length and temperature dependence. *
Laser induced temperature effects in multi-walled carbon nanotubes probed by Raman spectroscopy
physica status solidi (a), 2012
We examined the influence of continuous laser irradiation on as-prepared and oxidized multi-walled carbon nanotubes (MWCNTs) on the basis of Raman scattering. Differences between Raman spectra for both types of nanotube samples are shown. We evaluate the influence of the laser power density (LPD) on two main Raman modes (D and G) based on the position of the peaks, widths, and the relative intensity I D /I G ratio. Impurities and their interaction with nanotubes are crucial for interpretation of the measured effects. Oxidation, as well as the irradiation process, improves purity of samples. No structural changes of the tubes are observed. The Raman signal decrease is likely to originate from nanotube loss.
…, 2010
The extremely high thermal conductivity of individual carbon nanotubes, predicted theoretically and observed experimentally, has not yet been achieved for large nanotube assemblies. Resistances at tube-tube interconnections and tube-electrode interfaces have been considered the main obstacles for effective electronic and heat transport. Here we show that, even for infinitely long and perfect nanotubes with well-designed tube-electrode interfaces, excessive radial heat radiation from nanotube surfaces and quenching of phonon modes in large bundles are additional processes that substantially reduce thermal transport along nanotubes. Equivalent circuit simulations and an experimental self-heating 3ω technique were used to determine the peculiarities of anisotropic heat flow and thermal conductivity of single MWNTs, bundled MWNTs and aligned, free-standing MWNT sheets. The thermal conductivity of individual MWNTs grown by chemical vapor deposition and normalized to the density of graphite is much lower (κ MWNT = 600 ± 100 W m −1 K −1 ) than theoretically predicted. Coupling within MWNT bundles decreases this thermal conductivity to 150 W m −1 K −1 . Further decrease of the effective thermal conductivity in MWNT sheets to 50 W m −1 K −1 comes from tube-tube interconnections and sheet imperfections like dangling fiber ends, loops and misalignment of nanotubes. Optimal structures for enhancing thermal conductivity are discussed.
Temperature dependence of the Raman spectra of single-wall carbon nanotubes
Applied Physics Letters, 2000
Raman spectra of single-wall carbon nanotubes ͑SWCNTs͒ were measured at different temperatures by varying the incident laser power. The elevated temperature of the SWCNTs and multiwall carbon nanotubes ͑MWCNTs͒ is confirmed to be due to the presence of impurities, defects, and disorder. The temperature coefficient of the frequency of the C-C stretching mode E 2g ͑GM͒ and that of the radial breathing mode in the SWCNT were determined to be ϳϪ0.038 and ϳϪ0.013 cm Ϫ1 /K, respectively. It is found that the temperature coefficient of the GM in the SWCNT is larger than that of the MWCNT, highly oriented pyrolytic graphite, and the graphite. This is attributed to the structural characteristic of the SWCNT-a single tubular carbon sheet with smaller diameter.
Thermal Transport Measurements of Individual Multiwalled Nanotubes
Physical Review Letters, 2001
The thermal conductivity and thermoelectric power of a single carbon nanotube were measured using a microfabricated suspended device. The observed thermal conductivity is more than 3000 W͞K m at room temperature, which is 2 orders of magnitude higher than the estimation from previous experiments that used macroscopic mat samples. The temperature dependence of the thermal conductivity of nanotubes exhibits a peak at 320 K due to the onset of umklapp phonon scattering. The measured thermoelectric power shows linear temperature dependence with a value of 80 mV͞K at room temperature.
Thermal Investigations on Carbon Nanotubes by Spectroscopic Techniques
Applied Sciences
Carbon nanotubes (CNTs) thanks to their unique physical properties have been employed in several innovative applications particularly for energy storage applications. Certain technical features of carbon nanotubes, such as their remarkable specific surface, mechanical strength, as well as their electron and thermal conductivity are suitable for these applications. Furthermore, in order to produce a device, thermal treatment is needed and for this reason the trend of thermal decomposition of the tubes plays a key role in the integration process. The main purpose of this work was to characterize the thermal behavior of CNTs. In particular, we show the findings of an experimental study on CNTs performed by means of Fourier Transform InfraRed and Raman spectroscopy investigations. The collected FTIR and Raman spectra were analyzed by using two innovative procedures: spectral distance (SD) and wavelet cross correlation (XWT). From both analyses, a relaxation temperature value emerged of ...