title: Pentacene on Ag(111): correlation of bonding distance with intermolecular interaction and order.
abstract: We report coverage and temperature dependent bonding distances of vacuum-sublimed pentacene (PEN) submonolayers on Ag(111) obtained by the X-ray standing wave technique. The average vertical bonding distance of 2.98 Å at room temperature for 0.50 monolayer (ML) coverage increases to 3.12 Å for 0.75 ML due to competing intermolecular and adsorbate-substrate interactions. In contrast, decreasing the temperature from 295 to 145 K does not impact the bonding distance despite the concomitant transition from a "liquidlike" to an ordered molecular arrangement. In combination with X-ray photoelectron spectroscopy results, we could identify "soft chemisorption" with a subtle balance of molecule-molecule and substrate-molecule interactions as being responsible for this special adsorption behavior. Thus our study sheds light not only on the interface between PEN and Ag(111), but also on fundamental adsorption processes of organic adsorbates on metals in the context of chemi- and physisorption.
authors.affiliation: Soochow University-Western University Center for Synchrotron Radiation Research and Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , 199 Ren-Ai Road, Suzhou 215123, P.R. China.
authors.forename: Steffen
authors.initials: S
authors.lastname: Duhm
authors.forename: Christoph
authors.initials: C
authors.lastname: Bürker
authors.forename: Jens
authors.initials: J
authors.lastname: Niederhausen
authors.forename: Ingo
authors.initials: I
authors.lastname: Salzmann
authors.forename: Takuya
authors.initials: T
authors.lastname: Hosokai
authors.forename: Julien
authors.initials: J
authors.lastname: Duvernay
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kera
authors.forename: Frank
authors.initials: F
authors.lastname: Schreiber
authors.forename: Norbert
authors.initials: N
authors.lastname: Koch
authors.forename: Nobuo
authors.initials: N
authors.lastname: Ueno
authors.forename: Alexander
authors.initials: A
authors.lastname: Gerlach