Structural, Electronic and Transport Properties of Hybrid SrTiO3-Graphene and Carbon Nanoribbon Interfaces

Hybrid materials composed of different functional structural units offer the possibility of tuning both the thermal and electronic properties of a material independently. Using quantum mechanical calculations, we investigate the change of electronic and thermoelectric transport properties of graphene and hydrogen terminated carbon-nanoribbons (CNR) when these are placed on the SrTiO3 (001) surface (STO). We predict that both p-type and n-type composite materials can be achieved by coupling graphene/CNR to different surface terminations of STO. We show that the electronic properties of graphene and CNR are significantly altered on SrO-terminated STO but are preserved upon interaction with TiO2-terminated STO and that CNRs possess distinct electronic states around the Fermi level due to their quasi-one-dimensional nature, leading to a much higher calculated Seebeck coefficient than that of a pristine graphene sheet. Moreover, our calculations reveal that in the TiO2-SrTiO3/CNR system there is a favourable electronic level alignment between the CNR and STO, where the highest occupied molecular orbital of the CNR is positioned in the middle of the STO band gap, resembling n-type doping of the substrate. Our results offer design principles to guide the engineering of future hybrid thermoelectric materials and, more generally, nano-electronic materials comprising oxide and graphitic components.