Peer-Reviewed Journal Details
Mandatory Fields
Guaino, P;Cafolla, AA;Carty, D;Sheerin, G;Hughes, G
2003
August
Surface Science
An STM investigation of the interaction and ordering of pentacene molecules on the Ag/Si(111)-(root 3 x root 3)R30 degrees surface
Published
34 ()
Optional Fields
SCANNING-TUNNELING-MICROSCOPY LATERAL ORDER ADSORPTION BENZENE CU(111) PHTHALOCYANINE SPECTROSCOPY NAPHTHALENE DYNAMICS AU(111)
540
107
116
Scanning tunneling microscopy has been used to study the ordering of pentacene (C22H14) molecules on the Ag/Si(1 1 1)-(root3 x root3)R30degrees surface at room temperature. Two solid phases, S1 and S2, are observed at coverages of similar to0.35 monolayer (ML) and similar to1.0 ML respectively. It is shown that the solid phase S1 has a high-order commensurate lattice, Ag/Si(1 1 1)-(25 x 25)-pentacene, containing 75 molecules. The structure of this phase is determined from STM measurements at very low coverages where it is possible to image both the pentacene molecules and the structure of the Ag/Si(I 1 1) substrate. Two adsorption sites are identified, a three-fold hollow site at the centre of a Ag-trimer (CA-site) and a six-fold hollow site at the centre of the hexagonal arrangement of silver atoms (CB-site). A higher pentacene coverage of similar to1 ML lead to a molecular reorganization and forms a new commensurate structure Ag/Si(1 1 1)-(2 x 3)-pentacene, containing two molecules per unit cell. Because low energy electron diffraction patterns were not obtainable, for, this system, the structure of this second phase is determined by using the bias voltage as a tunable parameter to ''focus'' on either the molecular film or on the substrate. In this phase adsorption takes place exclusively on the Ag-trimer (CA) site and the CB-site is lost because of strong lateral molecule-molecule interactions. The role of competition between intermolecular and molecule-substrate interactions and the nature of the adsorption sites in determining the structure of the pentacene layers is discussed. (C) 2003 Elsevier B.V. All rights reserved.
AMSTERDAM
0039-6028
10.1016/S0039-6028(03)00751-9
Grant Details