The ultimate goal of molecular electronics is to create technologies that will complement—and eventually supersede - Si-based microelectronics technologies. To reach this goal, the field of single-molecule electronics is aiming at recognizing and characterizing single-molecule devices that mimic at least some of the behaviors of today's semiconductor components.

Carbon nanotubes have reached a quality that allows for stringent tests of theory. Applying high magnetic fields we perform transport spectroscopy on the first excess electron above the band gap. The observed single particle spectra allow to quantitatively probe the fine structure corrections to the simple Dirac Hamiltonian.