AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP33
LEED and STM Investigations of the Heteroepitaxy of Perylenetetracarboxylic-dianhydride (PTCDA) on Hexa-peri-benzocoronene (HBC) on Reconstructed Au(111) Surfaces

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: F. Sellam, TU Dresden, Institut fuer Angewandte Photophysik, Germany
Authors: T. Fritz, TU Dresden, Institut fuer Angewandte Photophysik, Germany
F. Sellam, TU Dresden, Institut fuer Angewandte Photophysik, Germany
T. Schmitz-Huebsch, TU Dresden, Institut fuer Angewandte Photophysik, Germany
M. Toerker, TU Dresden, Institut fuer Angewandte Photophysik, Germany
S. Mannsfeld, TU Dresden, Institut fuer Angewandte Photophysik, Germany
H. Proehl, TU Dresden, Institut fuer Angewandte Photophysik, Germany
K. Leo, TU Dresden, Institut fuer Angewandte Photophysik, Germany
Correspondent: Click to Email
The fabrication of multilayered films and superlattices consisting of different molecules has recently attracted considerable interest because of the prospective applications of those structures as active optoelectronic components in modern integrated devices. While the epitaxy of inorganic semiconductor heterojunctions is already well established, only little is known about the growth of organic heterostructures. We present the result of the combination of two OMBE (organic molecular beam epitaxy) grown materials of planar molecules, namely perylene-tetracarboxylic-dianhydride (PTCDA) and hexa-peri-benzocoronene (HBC). As substrate the Au(111) surface was chosen. Two complementary surface analysis methods which are low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) have been applied to characterize the growth of the ultrathin organic molecular heterojunction and to determine the epitaxial relation between the two lattices. In a first step, we investigated the growth of HBC on reconstructed Au(111) surfaces. Large domains which are defect free on the molecular scale are observed by STM. The LEED investigations reveal that HBC grows on reconstructed Au(111) in a commensurate hexagonal structure. The HBC lattice is rotated by 30° with respect to the Au[110] direction and therefore it appears only in a single domain orientation. In a second step, a monolayer of PTCDA was deposited on HBC and structurally characterized. The LEED and STM measurements show the well-known herringbone alignment of the PTCDA molecules, similar to that in the (102) bulk plane with two molecules in a rectangular unit cell, indicating the p2gg space symmetry group. Besides these findings, the pronounced two-dimensional Moiré pattern in the STM images was used to determine the relative orientation of the PTCDA unit cell with respect to the underlying HBC lattice, revealing a parallel orientation between the short PTCDA lattice vector and the HBC[10] direction.