Structural and Electronic Properties of the TTF/ZnO(10-10) Interface: Insights From Modeling

The structural and electronic properties of a tetrathiafulvalene (TTF) monolayer adsorbed onto the ZnO(10-10) surface are investigated by using two different quantum-chemical approaches, namely, density functional theory and the self-consistent charge density functional-parametrized tight binding method. The two approaches yield strong hybridization of the highest occupied molecular orbital (HOMO) level of the TTF molecules with band states of ZnO in the most stable interfacial geometric configuration, which results in the pinning of the corresponding orbital in the hybrid system and a significant charge transfer across the interface. As a consequence, the work function of ZnO is significantly reduced. We discuss these results in the context of the design of new hybrid opto-electronic devices, where the deposition of organic layers onto inorganic surfaces allows modulating the barrier height for charge injection.