Optical and Electronic Anisotropy of a π-Conjugated Molecular Monolayer on the Silicon(001) Surface

Abstract

The electronic and optical properties of an oriented monolayer of a π-conjugated molecule, 9,10phenanthrenequinone on a silicon(001) substrate were investigated. The adsorption of 9,10-phenanthrenequinone onto a single-domain, 4°-miscut Si(001) surface leads to an oriented monolayer film with intact π conjugation. Reflectance-difference spectroscopy (RDS) was used to probe the optical properties of the layer of 9,10phenanthrenequinone, and comparison spectra were obtained on a monolayer 1,2-cyclohexanedione, a nonconjugated molecule that has a nearly identical structure at the Si-O-C interface. RDS spectra of the 9,10-phenanthrenequinone monolayer show a strong absorption feature at 5.2 eV due to π-π * transitions within the molecule, while spectra of the nonconjugated analogue show no feature in this region. Further information about the electronic structure is provided by ultraviolet photoemission spectroscopy of the chemisorbed monolayers and by ultraviolet-visible absorption spectroscopy of the parent compounds. The experiments confirm that it is possible to create a macroscopic optical anisotropy in organic films on silicon surfaces using the Si(001) dimers to control the molecular orientation.

One-dimensional organic nanostructures: A novel approach based on the selective adsorption of organic molecules on silicon nanowires

“…Lastly, the new electronic structures observed at higher sample bias (>|1.5| V) are attributed to the electronic levels of the PQ molecules adsorbed on top of the SiNWs. The filled states region (negative bias) of the LDOS is in a good agreement with the PES, data published by Hacker and Hamers [14], in the case of PQ adsorbed on Si(0 0 1).…”

“…5a). Following the experimental work done by Fang et al and Hacker et al [13,14] as well as the first principle calculations performed by Hermann et al [15] on the adsorption of PQ on Si(0 0 1), we propose that an interaction occurs here between the Si dimers and the dicarbonyl group of the molecule via a specific chemical reaction so-called [4 + 2] cycloaddition. Such a reaction has been previously observed and well described between molecules containing a dicarbonyl or diene functions and Si surface dimers [16][17][18][19][20].…”

Molecular Electronic Junctions

“…Irreversibly Bonded Junctions on Silicon. The Hamers group has extensively investigated covalent bonding by olefin cycloaddition to silicon 107,108,110,115,[208][209][210][211][212][213][214] and diamond. 109,208,215 The Si(001) surface has SidSi double bonds in an ordered array when prepared in UHV.…”

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…To examine this question and also to make sure that all the compound used is present exclusively in a diketone form, Hamers group also investigated the chemistry of 9,10-phenanthrenequinone on Si(100)-2×1 [245,247]. The use of this compound addresses several important questions, including the competition between the Diels-Alder-type chemistry and stability of a complex aromatic system.…”