title: Molecular orientation in octanedithiol and hexadecanethiol monolayers on GaAs and Au measured by infrared spectroscopic ellipsometry.
abstract: Infrared spectroscopic ellipsometry was used for determination of molecular orientation and for lateral homogeneity studies of organic monolayers on GaAs and Au, the organic layer being either octanedithiol or hexadecanethiol (HDT). The laterally resolved measurements were performed with the infrared mapping ellipsometer at the synchrotron storage ring BESSY II. The molecular orientation within the monolayers was determined by optical model simulations of the measured ellipsometric spectra. Different tilt angles were obtained for the monolayers of HDT and octanedithiol on GaAs: 19 degrees and >30 degrees , respectively. The tilt angle of the methylene chains for HDT on Au substrate (22 degrees ) is similar to the 19 degrees tilt which was obtained for the HDT monolayers on GaAs, thus suggesting similar molecular ordering of the thiolates on both substrates.
authors.affiliation: ISAS-Institute for Analytical Sciences, Department Berlin, Albert-Einstein-Str. 9, 12489 Berlin, Germany. rosu@isas.de
authors.forename: Dana M
authors.initials: DM
authors.lastname: Rosu
authors.forename: Jason C
authors.initials: JC
authors.lastname: Jones
authors.forename: Julia W P
authors.initials: JW
authors.lastname: Hsu
authors.forename: Karen L
authors.initials: KL
authors.lastname: Kavanagh
authors.forename: Dimiter
authors.initials: D
authors.lastname: Tsankov
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schade
authors.forename: Norbert
authors.initials: N
authors.lastname: Esser
authors.forename: Karsten
authors.initials: K
authors.lastname: Hinrichs
mesh_terms: D001152:Arsenicals / Q000737:chemistry*; D005708:Gallium / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D008567:Membranes, Artificial; D013055:Spectrophotometry, Infrared; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D001152:Arsenicals; D008567:Membranes, Artificial; D013438:Sulfhydryl Compounds; C043055:gallium arsenide; C086974:hexadecanethiol; D006046:Gold; D005708:Gallium; C516316:1,8-octanedithiol