Band alignment in molecular devices: Influence of anchoring group and metal work function

Jian Guo Wang, Emil Prodan, Roberto Car, Annabella Selloni

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

Density functional theory calculations are carried out to investigate the electronic properties of molecular junctions formed by amine- and thiol-terminated alkane monolayers sandwiched between two metal (Au, Ag) electrodes. Based on extensive analysis of molecular monolayers of varying densities, we establish a relationship between the alignment of the molecular energy levels and the interface dipoles, which shows that the band alignment (BA) in the limit of long, isolated chains is independent of the link group and can be computed from a reference system of noninteracting molecule+metal molecule metal electrodes. The main difference between the amine and thiol linkers is the effective dipole moment at the contact. This is very large, about 4.5 D, for amine linkers, leading to a strong dependence of the BA on the monolayer density and a slow convergence to the isolated molecule limit. Instead, this convergence is relatively fast for S anchors due to the very small, ∼0.2 D, effective dipoles at the contacts.

Original languageEnglish (US)
Article number245443
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume77
Issue number24
DOIs
StatePublished - Jun 27 2008

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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