We report a combined ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) study of the electronic structure of aromatic self-assembled monolayers covalently bound to Si, using several different aromatic groups (phenyl, biphenyl, and fluorene) and binding groups (O, NH, and CH2). We obtain excellent agreement between theory and experiment, which allows for a detailed interpretation of the experimental results. Our analysis reveals a significant effect of the binding group on state hybridization at the organic/inorganic interface. Specifically, it highlights that lone-pair electrons in the binding atom facilitate hybridization between the aromatic system and the Si substrate, resulting in a significant induced density of interface states (IDIS). These interface states are manifested as a broadened HOMO peak in the experimental UPS data and are clearly observed in a theoretical spatially-resolved density of states map. This provides means to control the degree of coupling between substrate and molecule, which may prove useful in the design of transport across organic/inorganic interfaces.
|Number of pages||10|
|Journal||Journal of Electron Spectroscopy and Related Phenomena|
|State||Published - 1 Oct 2015|
Bibliographical noteFunding Information:
We thank Dov Diller (Bar-Ilan Univ.) for his help in synthesis, the Israel Science Foundation via its centers of Excellence program (CS, AV, LK, and DC), the Kimmel Centre for Nanoscale Science (LK and DC), and the Lise Meitner Minerva Center for Computational Chemistry (LK) for partial support. DC holds the Rowland and Sylvia Schaefer chair in Energy Research.
© 2015 Elsevier B.V.
- Aromatic monolayer
- Density functional theory
- Organic-inorganic interface
- Photoemission spectroscopy