Phthalocyanine Monolayers and Films on Copper

Monolayer structures and epitaxial growth of vapor-deposited crystalline phthalocyanine films on single crystal copper substrates were studied using low energy electron diffraction Ordered monolayers of three different phthalocyanines, copper, iron, and metal-free, were seen on two different faces of copper, the (111) and (100). The monolayer structures formed were different on the two crystal faces and the several phthalocyanines yield nonidentical monolayer structures. 

Ordered multilayer deposits were grown on both the Cu(l 11) and Cu(lOO) substrates. Electron beam damage to the phthalocyanine molecules was not observed. Space-charge effects due to electron bombardment were not apparent below an incident electron energy of 25 eV. 

The surface structures observed for the multilayer deposits of the phthalocyanines on both substrate faces, Cu(l 11) and Cu(lOO), were not those of any plane in the bulk crystal structure of the phthalocyanines. 

Deposition of Cu-phthalocyanine on a Pt(l 11) surface resulted in only poorly ordered monolayer structures and no ordering of multilayer structures. This demonstrates the importance of the details of the adsorbate-substrate interaction even for very large adsorbates which overlap tens of surface atoms. The absence of an ordered multilayer structure on this substrate indicates the role of an initially ordered mono-layer in controlling epitaxial growth. 

Ordered multilayer deposits of phthalocyanine molecules could be observed by low-energy electron diffraciton with no apparent electron beam induced chemical effects. This appears consistent with the general trend for molecules with highly conjugated electron systems to be more stable under electron bombardment than other organic molecules. 

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