▎ 摘　　要

Chemical vapor deposition (CVD) provides a synthesis route for large-area and high-quality graphene films. However, layer-controlled synthesis remains a great challenge on polycrystalline metallic films. Here, a facile and viable synthesis of layer-controlled and high-quality graphene films on wafer-scale Ni surface by the sequentially separated steps of gas carburization, hydrogen exposure, and segregation is developed. The layer numbers of graphene films with large domain sizes are controlled precisely at ambient pressure by modulating the simplified CVD process conditions and hydrogen exposure. The hydrogen exposure assisted with a Ni catalyst plays a critical role in promoting the preferential segregation through removing the carbon layers on the Ni surface and reducing carbon content in the Ni. Excellent electrical and transparent conductive performance, with a room-temperature mobility of approximate to 3000 cm2 V-1 s-1 and a sheet resistance as low as approximate to 100 O per square at approximate to 90% transmittance, of the twisted few-layer grapheme films grown on the Ni catalyst is demonstrated.