▎ 摘　　要

Chemical vapor deposition (CVD)-grown graphene films on Cu foils, exhibiting fine scalability and high quality, are still suffering from the adverse impact of surface contamination, i.e., amorphous carbon. Despite the recent successful preparation of superclean graphene through Cu-vapor-assisted reactions, the formation mechanism of amorphous carbon remains unclear, especially with regard to the functions of substrates. Herein, we have found that the crystallographic orientations of underlying metal substrates would determine the cleanness of graphene in such a way that slower diffusion of active carbon species on asformed graphene-Cu(100) surface is the key factor that suppresses the formation of contamination. The facile synthesis of clean graphene is achieved on the meter-sized Cu(100) that is transformed from the polycrystalline Cu foils. Furthermore, a clean surface of graphene on Cu(100) ensures the reduction of transfer-related polymer residues, and enhanced optical and electrical performance, which allows for versatile applications of graphene in biosensors, functioning as flexible transparent electrodes. This work would offer a promising material platform for the fundamental investigation and create new opportunities for the advanced applications of high-quality graphene films.