Microscopic origin of the apparent activation energy in diffusion-mediated monolayer growth of two-dimensional materials

Current trends indicate that mass production of high-quality, two-dimensional materials will likely be based on the use of on-surface synthesis (OSS) and/or chemical vapor deposition (CVD) on selected substrates. However, the success of these techniques heavily relies on a deeper understanding of terrace and perimeter diffusion of the adspecies across and around many self-generated, mobile clusters, and/or motionless islands with a variety of shapes (dendritic, compact, irregular, polygonal,...). We show that, for typical monolayer growth conditions at constant deposition rate, the total square distance traveled by all adsorbed particles departs from the total number of diffusion hops due to the onset of correlations between subsequent hops along the perimeters of a growing density of obstacles. As a result, we propose a new expression to determine the tracer diffusivity of the adparticles, directly providing a simple understanding of the temperature and coverage dependence of this observable. Most importantly, we describe the microscopic origin of the apparent diffusion barrier extracted from a typical Arrhenius plot at any given coverage.We acknowledge support by the Ramon y Cajal Fellowship Program by the Spanish Ministry of Science and Innovation, and the 2015/01 contract by the DIPC.Peer Reviewe