title: Chemisorption-induced gap states at organic-metal interfaces: benzenethiol and benzeneselenol on metal surfaces.
abstract: Valence electronic states of benzenethiol (C(6)H(5)SH) and benzeneselenol (C(6)H(5)SeH) in the gas, condensed, and chemisorbed phases were examined by ultraviolet photoemission spectroscopy, metastable atom electron spectroscopy, and first-principles calculations using density functional theory. C(6)H(5)SH is chemisorbed on Pt(111) and Au(111) substrates to form a thiolate (C(6)H(5)S), and C(6)H(5)SeH is bound on Pt(111) substrate to form a selenolate (C(6)H(5)Se). In all cases, chemisorption-induced gap states (CIGSs) appear just below the Fermi level (E(F)) of the substrate, yielding a metallic character around the anchor S and Se atoms. However, the local density at E(F) decreases considerably from the anchor atom to the benzene ring, because strong coupling between benzene π(1e(1g)) and S 3p(or Se 4p) in free molecules is apparently lifted upon chemisorption. In other words, thiolates and selenolates (especially C(6)H(5)S on Au(111)) act as poor mediators of the metal wave functions at E(F), which is closely related to electric conductance in the relevant metal-organic-metal junctions at zero bias.
authors.affiliation: Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro, Tokyo 153-8902, Japan. cmaoki@mail.ecc.u-tokyo.ac.jp
authors.forename: Masaru
authors.initials: M
authors.lastname: Aoki
authors.forename: Toyohiro
authors.initials: T
authors.lastname: Kamada
authors.forename: Keita
authors.initials: K
authors.lastname: Sasaki
authors.forename: Shigeru
authors.initials: S
authors.lastname: Masuda
authors.forename: Yoshitada
authors.initials: Y
authors.lastname: Morikawa
mesh_terms: D000327:Adsorption; D001555:Benzene Derivatives / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D016566:Organoselenium Compounds / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D011789:Quantum Theory; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D001555:Benzene Derivatives; D009942:Organometallic Compounds; D016566:Organoselenium Compounds; D010636:Phenols; D013438:Sulfhydryl Compounds; D010984:Platinum; C018846:benzeneselenol; D006046:Gold; C042983:thiophenol