Molecular materials, ranging from Carbon nanotubes to organic semiconductors, possess fascinating electronic properties, of great potential for both fundamental research and applications. In this talk, after briefly introducing the different research fields in which I am active, I will discuss the electronic transport properties of a variety of molecular compounds that permit to control experimentally the density of charge carriers, by means of electrostatic or chemical doping.
I will first focus on field-effect induced transport at the surface of molecular crystals, whose structural quality and chemical purity enable the investigation of the intrinsic properties of organic semiconductors, not limited by disorder. The richness of these materials is revealed by different phenomena, including the occurrence of band-like transport in the presence of strong (experimentally tunable) polaronic effects, the influence of electron-electron interaction at high density, the observation of ambipolar transport, and others.
I will then move on to classes of molecular systems in which we control the carrier density over a broad range, by intercalation with alkali atoms. Comparative studies of different molecular compounds reveal the occurrence of an insulator-metal-insulator transition with progressive doping, as well as the influence of the molecular orbitals occupied by the charge carriers on the conduction properties.
Finally, in the remaining time, I will touch upon our recent work on single walled nanotubes and briefly mention our related starting activity on graphene, i.e. single layers of graphite.