Energy band and vacuum level alignment at a semiconductor-molecule-metal interface

Abstract

We calculated the atomic structure and energy-level alignment at a representative Si-molecule-metal interface. The covalently bonded Si-molecule interface largely determines the overall band offset and the highest occupied molecular orbital position, while charge transfer across the metal-molecule interface induces localized π levels, even in the absence of covalent bonding to the metal. We propose a scheme for the vacuum level adjustment, consistent with the formation of interfacial dipoles and charge transfer to the molecular layer. The highest occupied π level of the molecule should be the main electronic state involved in the transport properties, while interface dipoles appear to be related to the interface-induced states.