We report on the observation of luminescence during electron field emission on singlewall and multiwall carbon nanotubes. Spectra acquired at different emitted currents, as well as the dependence of the luminescence intensity with the current, show that the light emission is not due to blackbody radiation or to current-induced heating. In fact, our results suggest that the light emission is caused by electron transitions between different electronic levels participating in the field emission.

• Received 27 February 1998

DOI:https://doi.org/10.1103/PhysRevLett.81.1441