Evolution of pentacene films on Ag(111):: Growth beyond the first monolayer

The formation and structure of pentacene films upon molecular beam deposition at room temperature onto a Ag(1 1 1) surface have been studied by means of SEM, XRD, TDS and NEXAFS. it is shown that multilayer films actually consist of separate crystalline islands revealing a bulk structure reported before by Siegrist et al. [T. Siegrist, C. Kloc, J.H. Schon, B. Batlogg, R.C. Haddon, S. Berg, G.A. Thomas, Angew. Chem. Int. Ed. 40 (2001) 1732]. Distinctly different pi*-resonances were observed in the C1s NEXAFS spectra of pentacene for the first monolayer and the crystalline films reflecting differences in the electronic coupling and the molecular orientation. Moreover, such characteristic pi*-signatures were used to monitor in situ the film evolution upon deposition indicating an immediate formation of crystalline islands on top of a chemisorbed wetting layer. (c) 2007 Elsevier B.V. All rights reserved.