Electronic coupling in fullerene-doped semiconducting carbon nanotubes probed by Raman spectroscopy and electronic transport

We investigate the electronic properties of individual fullerene peapods by combining micro-Raman spectroscopy and (magneto)-transport measurements on the same devices. We bring evidence that the encapsulated C60 molecules strongly modify the electronic band structure of semiconducting nanotubes in the vicinity of the charge neutrality point, including a rigid shift and a partial filling of the energy gap. Using a selective UV excitation of the fullerenes, we demonstrate that the electronic coupling between the contained C60 molecules and the containing carbon nanotube is strongly modified by the partial coalescence of the C60 and their distribution inside the tube. Our experimental results are supported by both numerical simulations of the Density of States and the measured conductance of carbon nanotubes with coalesced fullerenes inside.