Doping and phonon renormalization in carbon nanotubes

Abstract

We show that the Raman frequency associated with the vibrational mode at approximately 1,580 cm(-1) (the G mode) in both metallic and semiconducting carbon nanotubes shifts in response to changes in the charge density induced by an external gate field. These changes in the Raman spectra provide us with a powerful tool for probing local doping in carbon nanotubes in electronic device structures, or charge carrier densities induced by environmental interactions, on a length scale determined by the light diffraction limit. The G mode shifts to higher frequency and narrows in linewidth in metallic carbon nanotubes at large fields. This behaviour is analogous to that observed recently in graphene. In semiconducting carbon nanotubes, on the other hand, induced changes in the charge density only shift the phonon frequency, but do not affect its linewidth. These spectral changes are quantitatively explained by a model that involves the renormalization of the carbon nanotube phonon energy by the electron-phonon interaction as the carrier density in the carbon nanotube is changed.

Optical Properties of Single‐Walled Carbon Nanotubes Doped in Acid Medium

“…[9] Regarding the G-mode region, it is widely known, [10] that the doping of single-walled carbon nanotubes leads to a strong upshift and a moderate suppression of G-mode. However, no www.advancedsciencenews.com www.pss-b.com upshift of the G mode was observed in this work after adding of HCl to the suspension, although, the suppression of G-mode is seen.…”

High-throughput optical imaging and spectroscopy of individual carbon nanotubes in devices

“…We calibrated the gating efficiency of our field-effect device by characterizing the gatedependent G-mode Raman peak in non-armchair metallic carbon nanotubes 1 . Figure S1 shows one calibration example from a (13, 1) nanotube on 90nm SiO 2 /Si substrate with back-gate fieldeffect transistor geometry.…”

“…S1b and S1c, respectively. From the theoretical fitting, we can deduce a gating efficiency of 0.013 hole/(nm.V) for line charge density in this (13,1) nanotube (diameter =1.1 nm). For nanotubes of different diameter, the classic capacitance scales with 1/ln(4t/d), where t is thickness of dielectric layer and d is the nanotube diameter.…”

“…They are promising materials for next generation nanoelectronic and nano-photonic devices, including field-effect transistors, light emitters and photocurrent/photovoltaics device [1][2][3][4][5][6][7] . Currently nanotube research faces two outstanding challenges: (1) achieving chirality-controlled nanotube growth and (2) understanding chirality-dependent nanotube device physics.…”

“…Two paramount challenges in carbon nanotube research are achieving chiralitycontrolled synthesis and understanding chirality-dependent device physics [1][2][3][4][5][6][7] . Highthroughput and in-situ chirality and electronic structural characterization of individual carbon nanotubes is crucial for addressing these challenges.…”