title: Mixed self-assembled monolayers of azobenzene photoswitches with trifluoromethyl and cyano end groups.
abstract: Mixed self-assembled monolayers (SAMs) of alkanethiolates carrying azobenzene chromophores with either a trifluoromethyl or a cyano substituent have been studied. High-resolution x-ray photoelectron spectroscopy proves that the ratio of adsorbed molecules can be arbitrarily adjusted via the molar fractions in solution. As a function of these molar fractions core level shifts are observed which are attributed to local work-function changes. By simulating the electric dipole field distribution, the continuous core level shifts are ascribed to a homogeneous mixture of molecules with different end groups adsorbed on adjacent lattice sites. Near-edge x-ray absorption fine structure measurements reveal formation of well-ordered SAMs. Despite the difference in dipole moment of the end groups, the molecular tilt and twist angles are identical for both single-component SAMs and a 1:1 mixed SAM.
authors.affiliation: Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Brete
authors.forename: Daniel
authors.initials: D
authors.lastname: Przyrembel
authors.forename: Christian
authors.initials: C
authors.lastname: Eickhoff
authors.forename: Robert
authors.initials: R
authors.lastname: Carley
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Freyer
authors.forename: Karsten
authors.initials: K
authors.lastname: Reuter
authors.forename: Cornelius
authors.initials: C
authors.lastname: Gahl
authors.forename: Martin
authors.initials: M
authors.lastname: Weinelt