AVS 49th International Symposium
    Processing at the Nanoscale Thursday Sessions
       Session PN+SS-ThM

Paper PN+SS-ThM4
Reversible Layer Phase Transition Controlled by the Scanning Tunneling Microscope Tip

Thursday, November 7, 2002, 9:20 am, Room C-109

Session: Patterning and Functionalization
Presenter: S. Berner, University of Basel, Switzerland
Authors: S. Berner, University of Basel, Switzerland
M. de Wild, University of Basel, Switzerland
L. Ramoino, University of Basel, Switzerland
S. Schintke, University of Basel, Switzerland
H. Suzuki, Kansai Adv. Res. Center, Japan
A. Baratoff, University of Basel, Switzerland
H.-J. Guentherodt, University of Basel, Switzerland
T.A. Jung, Paul Scherrer Institute, Switzerland
Correspondent: Click to Email
Sub-phthalocyanine (SubPc) on Ag(111) shows a complex phase behaviour of the growing first molecular monolayer. With increasing layer coverage, 2D lattice gas, condensed honeycomb superstructure and hexagonal close packed layers are observed. A previous study of SubPc on Ag(111) dealt with the coexistence of the honeycomb superstructure and the 2D lattige gas and showed the high mobility of individual SubPc molecules at room temperature.@footnote 1@ The complex phase behaviour is a general consequence of the repulsive nearest neighbour interaction between individual molecules and the diffusion at room temperature. In this work we studied SubPc layers with a coverage in the order of 0.7 monolayers on Ag(111) with room temperature scanning tunneling microscopy (STM). On large terraces the SubPc molecules form a hexagonal close packed (hcp) superstructure. However, experimental sequences on confined terrace areas (vacancy islands with diameters of 30-80 nm introduced by sputter defects) reveal interesting details about the condensation and evaporation of molecular islands on a nanometer scale. In such vacancy islands reversible phase transitions between 2D mobile and 2D condensed (hcp) phases could be controlled by the STM tip. In addition, rotational flipping of the orientation of condensed islands between two different substrate lattice registries occurred. Different microscopic mechanisms are discussed in the context of this newly observed complex behaviour. . @FootnoteText@ @footnote 1@ S. Berner, M. Brunner, L. Ramoino, H. Suzuki, H.-J. Guentherodt, and T.A. Jung, Chem. Phys. Lett. 348 (2001) 175.