Carbonization-driven motion of Si islands on epitaxial graphene

We investigate structural changes in Si islands deposited at room temperature on epitaxial few-layer graphene on SiC(0001) during subsequent annealing. Annealing causes the Si islands move on epitaxial graphene thicker than monolayer with monolayer-deep trenches left behind. In contrast, Si islands do not form trenches on monolayer graphene, but the Si atoms are intercalated to form quasifreestanding bilayer graphene. The islands which terminated their motion are made of SiC. During annealing, Si islands are carbonized into SiC islands by incorporating carbon atoms from graphene, resulting in the etching of graphene. The carbonization reaction of Si is a driving force of the motion of the Si islands.