AFM induced diffusion of large scale mobile HOPG defects

Abstract

Defects on crystal and/or thin film surfaces play an important role in their physical and chemical properties. Diffusion or motion of such structures results in microstructural dynamic changes. The diffusion of single atom/point defects were previously reported, due to the difficulty of observation, the motion of large-scale defects (the defect consist of multiple missing atoms) using combination of consecutive images has not been possible since today. For the first time, the diffusion of three mobile large-scale highly oriented pyrolytic graphite monolayer defect domains is reported using non-contact atomic force microscopy in ultra-high vacuum conditions. It was suspected that the diffusion of the defects was triggered by the rastering motion of the tip of atomic force microscope. It was evidenced that the diffusion of large defects is shown to be size-dependent, with smaller defects moving with higher speeds than larger defects. The diffusion results fit well with the models previously reported for the diffusion of particles for varying sizes and indicates that the diffusion of defects and particles show similar behaviours.