Electrically driven thermal light emission from individual single-walled carbon nanotubes

Light emission from nanostructures exhibits rich quantum effects and has broad applications. Single-walled carbon nanotubes (SWNTs) are one-dimensional metals or semiconductors in which large numbers of electronic states in narrow energy ranges, known as van Hove singularities, can lead to strong spectral transitions(1,2). Photoluminescence and electroluminescence involving interband transitions and excitons have been observed in semiconducting SWNTs3-9, but are not expected in metallic tubes owing to non-radiative relaxations. Here, we show that, under low bias voltages, a suspended quasi-metallic SWNT (QM-SWNT) emits light owing to Joule heating, displaying strong peaks in the visible and infrared, corresponding to interband transitions. This is a result of thermal light emission in a one-dimensional system, in stark contrast with featureless blackbody-like emission observed in large bundles of SWNTs or multiwalled nanotubes(10-12). This allows for probing of the electronic temperature and non-equilibrium hot optical phonons in Joule-heated QM-SWNTs.