Scanning force microscopy study of ultrathin films of nickel-phthalocyanine on graphite

Small amounts of purified nickel-phthalocyanine (Ni-PC) have been deposited at room temperature in ultrahigh vacuum onto highly oriented pyrolytic graphite, and studied "in situ" and "ex situ" (in air) with two different atomic force microscopes. The measurements have been taken on samples as prepared either subsequently annealed at 300 degrees C. The growth mode is not uniform; the PC molecules coalesce into small submicrometric crystallites in the critical sire range where the transition from the alpha to the beta crystalline phase of phthalocyanines takes place. We show images of both alpha-like and beta-like crystallites. A contact mode AFM image of an alpha-like crystallite showing intramolecular resolution is also presented.