The surface structures of phthalocyanine monolayers and vapor-grown films: A low-energy electron diffraction study

Abstract

Monolayer structures and epitaxial growth of vapor-deposited crystalline phthalocyanine films on single-crystal copper substrates were studied using low-energy electron diffraction. At monolayer coverage, ordered layers of copper-, iron-, and metal-free phthalocyanines were observed on both Cu(100) and Cu(111). With increasing film thickness, ordered multilayer structures of these phthalocyanines were also seen on both substrates at 300 K surface temperature. All three phthalocyanines had identical monolayer and multilayer surface structures on Cu(100). On the Cu(111) substrate, the three phthalocyanines exhibited slightly different surface structures, indicating the importance of the central metal atom in the interaction with the substrate that influences the monolayer surface structure and the ordering during crystal growth. The multilayer crystalline films did not have surface structures characteristic of the bulk crystal structure but rather had a surface unit mesh compatible with a single molecule per unit mesh, oriented parallel to the surface. Electron beam damage and space charge effects were negligible for film thicknesses up to 500–1000 Å.