Texture-engineered fabrication of ultraflat, 6-inch single-crystal Cu(111) wafers

Ultraflat, single-crystal Cu(111) thin films are widely regarded as ideal epitaxial substrates for synthesizing two-dimensional single crystals for ease of subsequent transfer and device integration. However, the fabrication of Cu(111) remains hindered by a lack of scalable and reliable technique to eliminate in-plane twin boundaries (TBs) in final films. Here, we present a method to address TB issues for harvesting ultraflat, TB-free Cu(111) wafers, which also enable the growth of high-quality, single-crystal graphene wafers. It has been revealed that the deposition of Cu films with designed texture would enable the selective abnormal grain growth of specific Cu(111) during high-temperature annealing, allowing for the production of 6-inch TB-free Cu(111) wafers with high crystallinity (misorientation angle of 0.48°), flatness (R_a = 0.34 nm), and scalability (25 wafers per batch). As-harvested graphene exhibits excellent electronic quality and wafer-scale uniformity, with an average carrier mobility of 10,093 square centimeters per volt per second and sheet resistance of 905 ohm per square with 3.5% deviation over entire wafer.