Characterization of Organic Epitaxial Films by Atomic Force Microscopy

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Abstract
The initial stage of the epitaxial growth of vanadyl-phthalocyanine (VOPc) films on alkali halides (AH) and MoS2 was studied by atomic force microscopy. Each grain grew epitaxially on the surface with its crystal axis parallel to that expected from the molecular arrangements determined by reflection high energy electron diffraction. The growth mode of the VOPc films on AH was the Volmer- Weber type. Although the height of the grains increased with the deposition time, the grains hardly enlarged in the lateral direction. The shape of grains was affected even by steps with atomic height on AH. On the other hand, the nuclei grew rapidly in the lateral direction on MoS2. The diffusion length of VOPc on MoS2 was estimated to be six times as long as that on KBr at room temperature. Large domains with flat surfaces were observed on a MoS2 surface when the substrate temperature was kept at 100°C during film growth.