Influence of substrate sapphire orientation on direct CVD growth of graphene

Abstract

Graphene is grown directly on c-, a-, m-, and r-plane sapphire substrates by chemical vapor deposition, and their structures and electrical properties are compared. The obtained graphene is always polycrystalline, but the grain size is dependent on the sapphire surface orientation. The largest and smallest grains respectively appear on the m- and c-planes, and the graphene grown on the a- and r-planes has intermediate grain sizes. The carrier mobility is the largest for the graphene grown on the m-plane, indicating that the grain boundaries make a significant impact on the carrier transport as scattering centers. Nevertheless, the room-temperature Hall effect mobility measured for the mm-sized m-plane samples reaches 7000 cm2V-1s-1. m-plane sapphire is promising as an insulating substrate for direct graphene growth.