Combined electrical transport and Raman measurements of individual single-walled carbon nanotubes

Local photo-oxidation of individual single walled carbon nanotubes probed by femtosecond four wave mixing imaging

Photo-oxidation of individual, air-suspended single walled carbon nanotubes (SWCNTs) is studied by femtosecond laser spectroscopy and imaging. Individual SWCNTs are imaged by four wave mixing (FWM) microscopy under an inert gas (Ar or N2) atmosphere. When imaging is performed in an ambient air atmosphere, the decay of the FWM signal takes place. Electron microscopy shows that SWCNTs are not destroyed and the process is attributed to photoinduced oxidation reactions which proceed via a non-linear excitation mechanism, when irradiation is performed with ∼30 fs pulses in the visible spectral region (500-600 nm). Photo-oxidation can be localized in specific regions of SWCNTs within optical reso…

Femtosecond four-wave-mixing spectroscopy of suspended individual semiconducting single-walled carbon nanotubes.

Femtosecond four-wave-mixing (FWM) experiments of individual suspended semiconducting single-walled carbon nanotubes (SWCNTs) are presented. The chiral indices of the tubes were determined by electron diffraction as (28,14) and (24,14) having diameters of 2.90 and 2.61 nm, respectively. The diameter and semiconducting character of the tubes were additionally confirmed by resonance Raman measurements. The FWM signal showed electronic response from the SWCNTs. The results demonstrate that ultrafast dynamics of individual SWCNTs can be studied by FWM spectroscopies.

Second-harmonic Generation Microscopy of Carbon Nanotubes

We image an individual single-walled carbon nanotube (SWNT) by second-harmonic generation (SHG) and transmission electron microscopy and propose that SHG microscopy could be used to probe the handedness of chiral SWNTs.

Raman Spectroscopy and Low-Temperature Transport Measurements of Individual Single-Walled Carbon Nanotubes with Varying Thickness

We have investigated two metallic and one semiconducting individual single-walled carbon nanotubes (SWNT) and one bundle of two semiconducting nanotubes with a diameter range 1.1−2.9 nm with Raman spectroscopy and low-temperature electric transport measurements. With these two methods, we obtain mutually independent measurements on the basic properties of a specific nanotube. In particular, we obtain data on metallic and semiconducting properties. Evidence of a small band gap for one metallic tube was obtained. For the semiconducting SWNTs with diameters of 2.7−2.9 nm, a special resonance condition was observed which causes an anomalous intensity ratio for the two components of the G-band. …

Measurement of optical second-harmonic generation from an individual single-walled carbon nanotube

We show that optical second-harmonic generation (SHG) can be observed from individual single-walled carbon nanotubes (SWCNTs) and, furthermore, allows imaging of individual tubes. Detailed analysis of our results suggests that the structural noncentrosymmetry, as required for SHG, arises from the non-zero chiral angle of the SWCNT. SHG thus has potential as a fast, non-destructive, and simple method for imaging of individual nanomolecules and for probing their chiral properties. Even more, it opens the possibility to optically determine the handedness of individual SWCNTs.

Ultra-Low Noise Multiwalled Carbon Nanotube Transistors

We report an experimental noise study of intermediate sized quasi ballistic semiconducting multiwalled carbon nanotube (IS-MWCNT) devices. The noise is two orders of magnitude lower than in singlewalled nanotubes (SWCNTs) and has no length dependence within the studied range. In these channel limited devices with small or negligible Schottky barriers the noise is shown to originate from the intrinsic potential fluctuations of charge traps in the gate dielectric. The gate dependence of normalized noise can be explained better using ballistic the charge noise model rather than diffusive McWhorter’s model. The results indicate that the noise properties of IS-MWCNTs are closer to SWCNTs than th…

Experimental characterization of electronic, structural and optical properties of individual carbon nanotubes

Multimodal nonlinear imaging of suspended carbon nanotubes using circular polarizations

In this work, multimodal nonlinear microscopy of suspended CNTs using circular polarizations (CP) was reported. Significant variations in the SHG and THG signals of the CNTs between left hand circular polarization (LHCP) and right hand circular polarization (RHCP) were observed. The variations in the nonlinear signals can be associated to the unique properties of the CNTs such as chirality.

Background-Free Second-Harmonic Generation Microscopy of Individual Carbon Nanotubes

We use polarized second-harmonic generation (SHG) microscopy to investigate pristine air-suspended carbon nanotubes (CNT). We show that SHG originates from CNT chirality, allowing also different response for the two circular polarizations of fundamental light.

Electronic transport in intermediate sized carbon nanotubes

We have studied systematically basic transport properties of multiwalled carbon nanotubes in a relatively unexplored diameter range, corresponding to tubes just slightly larger than single- or double-walled tubes to tubes up to 17 nm in diameter. We find in all the smaller tubes a gap in the transport data which increases with decreasing tube diameter. Within the gap region of several tubes, negative differential resistance was observed at small or moderate biases and at bias values that scaled inversely with the tube diameter. For this latter type of behavior of the conductance, we tentatively propose interlayer resonant tunneling as the cause.

Electronic transport measurements and Raman spectroscopy on carbon nanotube devices

An individual single wall carbon nanotube (SWCNT) device has been fabricated and measured using both low temperature transport and Raman measurements. With these mutually independent methods we can study the correlation between the techniques on semiconducting or metallic behavior of the tube. Furthermore, we study the structure of the nanotube by probing Raman measurements at different spots along the tube axis.