▎ 摘　　要

Adsorption behaviors of carbon atoms on Al2O3(0001) are investigated to understand the graphene growth in its initial stage. For the most stable structure of carbon on sapphire, C-O binding is analyzed by examining projected density of states. Increased carbon atoms are found to form cluster structures such as chain-like or distorted graphene-like one. Due to strong C-O binding, at least one carbon atom of the cluster structures binds an oxygen atom of the sapphire surface. Combined with C-C interaction, this result may explain that carbon atoms on sapphire form nanocrystalline graphitic structures within a limited area, observed in experiment.