Field of Expertise: Advanced Material Science
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Field of Expertise: Advanced Material Science | |
Using orbital tuning in self-assembled monolayers to build molecular quantum-well structures The possibility of controlling interface properties “at will” holds a high promise for hybrid electronics applications. Covalently-bonded self-assembled monolayers (SAMs) are very well suited for such interface modifications, as they offer a high flexibility regarding the design of their electronic properties. For example, the distribution of dipolar groups along phenylthiol-based self-assembled monolayers has been shown to cause a modification of the electron wave-function and the vacuum level.[1] In particular, states like the highest occupied molecular orbital (HOMO) and the lowest unoccupied orbital (LUMO) get shifted in energy and localized on opposite ends of the molecular layer.[2] The latter can, for example, be interesting for separating electrons and holes in a device. Building on these results, we here describe band-structure calculations using density functional theory on phenylthiolate-based and thiophenethiolate-based SAMs where dipolar groups (in the present case pyrimidine rings) are distributed along the SAMs. The aim of the latter is to gain full control of orbital localization and intra-layer energy-level offsets, which can be used for realizing SAM-based quantum-well structures. Our results show that this strategy of modifying the energetic structure works successfully and that collective electrostatic effects can help in achieving the desired control of the electronic properties. |