▎ 摘　　要

Graphene is a hexagonally bonded sheet of carbon atoms that exhibits superior transport properties with a velocity of 10(8) cm/s and a room-temperature mobility of >15 000 cm(2)/V s. How to grow gate dielectrics on graphene with low defect states is a challenge for graphene-based nanoelectronics. Here, we present the growth behavior of Al(2)O(3) and HfO(2) films on highly ordered pyrolytic graphite (HOPG) by atomic layer deposition (ALD). To our surprise, large numbers of Al(2)O(3) and HfO(2) nanoribbons, with dimensions of 5-200 nm in width and >50 mu m in length, are observed on HOPG surfaces at growth temperature between 200 and 250 degrees C. This is due to the large numbers of step edges of graphene on HOPG surfaces, which serve as nucleation sites for the ALD process. These Al(2)O(3) and HfO(2) nanoribbons can be used as hard masks to generate graphene nanoribbons or as top-gate dielectrics for graphene devices. This methodology could be extended to synthesize insulating, semiconducting, and metallic nanostructures and their combinations. (C) 2008 American Institute of Physics.