title: Determination of the electronic structure of self-assembled L-cysteine/Au interfaces using photoemission spectroscopy.
abstract: The electronic and chemical structure of the interface between the amino acid L-cysteine and Au was determined by photoemission spectroscopy (PES). L-cysteine was deposited by repeatedly dipping Au substrates into solutions of L-cysteine in methanol with various concentrations. To enable repeat deposition without significant contamination, the dipping procedure was performed in a glovebox directly connected to the ultrahigh vacuum (UHV) chamber in a N2 atmosphere. X-ray photoemission spectroscopy (XPS) measurements between deposition steps allowed to characterize the chemical interaction at the interface to be characterized. Ultraviolet photoemission spectroscopy (UPS) measurements yielded the orbital line-up at the interface as well as the highest occupied molecular orbital (HOMO) structure of L-cysteine. The charge injection barrier between the L-cysteine HOMO and the Au Fermi level was found to be 3.0 eV. The interface dipole between the Au substrate and the L-cysteine overlayer was determined to be 1.03 eV. The results also indicate the formation of an interface state approximately 1.5 eV above the HOMO of the L-cysteine.
authors.affiliation: Department of Electrical Engineering, University of South Florida, Tampa, Florida 33620, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Beerbom
authors.forename: R
authors.initials: R
authors.lastname: Gargagliano
authors.forename: R
authors.initials: R
authors.lastname: Schlaf
mesh_terms: D001272:Atmosphere; D003545:Cysteine / Q000737:chemistry*; D004583:Electrons; D006046:Gold / Q000737:chemistry*; D008956:Models, Chemical; D009584:Nitrogen / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods*; D013237:Stereoisomerism; D013499:Surface Properties; D013816:Thermodynamics; D014965:X-Rays
chemical_list: D006046:Gold; D003545:Cysteine; D009584:Nitrogen