LAYER-BY-LAYER QUASI-EPITAXIAL GROWTH OF A CRYSTALLINE ORGANIC THIN-FILM

We use reflection high energy electron diffraction and grazing inciden ce X-ray diffraction to study films of the archetype crystalline organ ic material: 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) grow n on Au(111) by organic molecular beam deposition. Although the PTCDA lattice is significantly mismatched to the Au(111) substrate, the film s are orientationally aligned and have a well defined film thickness, providing evidence for layer-by-layer ''quasi-epitaxial'' growth. Furt hermore, we have performed the first characterization of the molecular level disorder in these films, and have determined the presence of a significant (3.8%) strain in the 2D lattice parameters.