Nanomechanical oscillations in a single-C60 transistor

The motion of electrons through quantum dots is strongly modified by single-electron charging and the quantization of energy levels(1,2). Much effort has been directed towards extending studies of electron transport to chemical nanostructures, including molecules(3-8), nanocrystals(9-13) and nanotubes(14-17). Here we report the fabrication of single-molecule transistors based on individual C-60 molecules connected to gold electrodes. We perform transport measurements that provide evidence for a coupling between the centre-of-mass motion of the C-60 molecules and single-electron hopping(18)-a conduction mechanism that has not been observed previously in quantum dot studies. The coupling is manifest as quantized nano-mechanical oscillations of the C-60 molecule against the gold surface, with a frequency of about 1.2 THz. This value is in good agreement with a simple theoretical estimate based on van der Waals and electrostatic interactions between C-60 molecules and gold electrodes.