Morphology and Structure Transitions of Copper Hexadecafluorophthalocyanine (F₁₆CuPc) Thin Films

Abstract

The thickness-dependent morphology and structure transitions of pristine and thermally annealed F 16 CuPc thin films deposited from the vapor phase by organic molecular beam deposition have been studied with use of atomic force microscopy, scanning electron microscopy, and X-ray diffraction. Pristine films show clear morphology transitions with increasing thickness, changing from spherical-like crystals to flexible-fiber-like crystals via standing-up needle-like crystals. Two different roughening processes are identified: kinetic roughening for films <30 nm thick (scaling exponent, β ≈ 0.123) and rapid roughening for films ≥30 nm thick (β ≈ 3.089). Thicker pristine films are composed of two crystal layers: a spherical-crystal layer and a flexible-fiber-crystal layer. Controlled thermal annealing leads to further reorganization of the packing geometry and large crystals dominate the resulting film morphology. Mechanisms are proposed for the structure and morphology transitions.