Development of the Tangential Mode in the Raman Spectra of SWCNT Bundles during Electrochemical Charging

• Published in: Nano letters Vol. 8; no. 4; pp. 1257 - 1264
• Main Authors: Kalbac, M, Kavan, L, Dunsch, L, Dresselhaus, M. S
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.04.2008
• Subjects: Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials science; Nanoscale materials and structures: fabrication and characterization; Nanotubes; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Surface and interface electron states; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Singlewalled nanotube; Electrochemical properties; Asymmetry; Optical properties; Doping; Thermogravimetry; Plasmons; Anomaly; Raman spectroscopy
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl073104h

The detailed analysis of the in situ Raman spectroelectrochemical behavior of single walled carbon nanotube (SWCNT) bundles is presented. The Raman modes of metallic SWCNTs exhibit striking changes even before the potential of the first van Hove singularity is achieved. Special attention has been paid to the development of the tangential (TG) mode broadening, which subsequently vanishes if the potential is shifted away from V = 0. The tangential mode band has been fitted by four components. During the electrochemical doping, three components of the tangential mode follow the predictions of a theoretical model for the LO modes of metallic tubes based on the Kohn anomaly. On the other hand, the behavior of the fourth component is consistent with a model based on electron−plasmon coupling. The TO mode of metallic tubes has been identified only at a doping level corresponding to 1.0 V or above. Our results also indicate an asymmetry in the behavior of the TG mode for positive electrode potentials relative to negative ones.