Light absorption leads inevitably to electronic excitation and inelastic electron scattering, creating phonons and resulting in the increase of the lattice temperature. By using photons with energies significantly above the fundamental band gap of the electronic states, one can use the energy released in the inelastic electronic decay process to efficiently heat carbon nanotubes. We show that double wall carbon nanotubes can be heated up to 1300C using UV irradiation (338nm) by measuring the phonon line broadening as a function of irradiation intensity. The thermal expansion in double wall carbon nanotubes is found to lead to structural constrains between the two tube walls as evidenced by the spectral shifts of the optical phonon band of the internal end external tube. Differences are also found in the coupling of the optical phonon to acoustic phonons. UV photon absorption has the advantage that tubes of a given orientation can be selectively heated on specified positions on the substrate making it a powerful tool for processing of carbon nanotubes on surfaces.
Journal: TechConnect Briefs
Volume: 1, Technical Proceedings of the 2007 NSTI Nanotechnology Conference and Trade Show, Volume 1
Published: May 20, 2007
Pages: 17 - 20
Industry sector: Advanced Materials & Manufacturing
Topics: Carbon Nano Structures & Devices