We report on temperature-programmed growth of graphene islands on Ru (0001) at annealing temperatures of 700 ℃,800 ℃,and 900 ℃.The sizes of the islands each show a nonIinear increase with the annealing temperature.In 700 ℃ and 800 ℃ annealings,the islands have nearly the same sizes and their ascending edges are embedded in the upper steps of the ruthenium substrate,which is in accordance with the etching growth mode.In 900 ℃ annealing,the islands are much larger and of lower quality,which represents the early stage of Smoluchowski ripening.A longer time annealing at 900 ℃ brings the islands to final equilibrium with an ordered moiré patte.Our work provides new details about graphene early growth stages that could facilitate the better control of such a growth to obtain graphene with ideal size and high quality.