Investigation of non-equilibrium phonon populations in biased metallic single-walled carbon nanotubes (SWCNTs)

• Applicant: Professor Dr. Ralph Krupke, since 10/2013
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2009 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 85215188

The generation of so called hot-phonons in biased metallic single-walled carbon nanotubes will be experimentally explored. The influence of electron-phonon coupling on the resistance of metallic single-walled carbon nanotubes is relevant to high-current applications such as interconnectors. In the regime of high-bias, accelerated electrons in metallic nanotubes relax under the emission of high-energy phonons. These phonons will accumulate in the nanotube if their generation rate exceeds their relaxation rate. Under these conditions, the increase in population can be detected by Raman spectroscopy where the spectrum will show an increase in the intensity of a particular mode in the high energy region. Using Bose-Einstein statistics one can then calculate the phonontemperature of these phonons. An unresolved and important issue of hot-phonons generation concerns the spatial distribution of the phonons along the single-walled carbon nanotube. In this project we attempt to answer the following questions: (i) Is the generation of the non-equilibrium phonons a local effect? (ii) Must the tube be suspended to reach the predicted phonon-temperature of a few thousand Kelvin and (iii) Does the signal in the high-energy part of the spectrum (anti-Stokes signal) arise from freely suspended tube-segments or from the entire tube length?For the experiment we propose to use Near-field Raman spectroscopy and far-field Raman microscopy operating in a slit-limited-aperture mode, which provide the required spatial resolution of less than 50 nm, in combination with a nanotube specific electron transport measurement setup.

• DFG Programme: Research Grants
• Participating Person: Professor Dr.-Ing. Horst Hahn
• Ehemalige Antragstellerin: Dr. Matti Oron-Carl, until 10/2013