▎ 摘　　要

NOVELTY - A substrate is made of iron-cobalt-nickel-copper alloy (I), and has thickness of less than 0.3 mm, and surface roughness of less than 1000. USE - Substrate is used for preparing high-quality graphene (claimed). ADVANTAGE - High-quality graphene formed using the substrate has excellent continuity, high crystallization degree, and less defects and wrinkles, and is transferred to the silica/silicon wafer without polymer assistance. DETAILED DESCRIPTION - A substrate is made of iron-cobalt-nickel-copper alloy of formula: FeCoNiCun (I), and has thickness of less than 0.3 mm, and surface roughness of 1000 nm or less. n = 0.1-0.3 by molar ratio. INDEPENDENT CLAIMS are included for the following: (1) preparation of the substrate, which involves weighing a predetermined mass of iron, cobalt, nickel and copper bulk metal raw materials, adding the weighed raw materials to a water-cooled copper mold smelting tank, repeatedly vacuuming, introducing argon, simultaneously melting the elemental metal to reduce the oxygen content in the cavity, selecting predetermined melting temperature and time, turning the alloy block after the alloy is fully mixed, repeating above process several times, comprising obtained sample alloy block into a round cake with displacement parameter of 1-10 mm/minute, and maximum test force is 160 kN, such that the sample undergoes a small amount of plastic deformation without cracking, cutting obtained round cake-shaped alloy block with maximum diameter of 2-5 cm into multiple components of alloy flakes with a thickness of 0.4 mm using a wire cutting machine, mechanically polishing, then polishing, ultrasonically cleaning for 30 minutes, and obtaining a clean iron-cobalt-nickel-copper alloy high-entropy sheet with a single mirror surface; and (2) preparation of high-quality graphene, which involves annealing iron-cobalt-nickel-copper alloy high-entropy sheet at 1040 degrees C for 15 minutes, then growing graphene in a sliding high-temperature tube furnace by chemical vapor deposition method using 300 sccm argon as a carrier gas, 20 sccm hydrogen as a reducing gas, and 4 sccm methane as a carbon source, by heating at rate of 35 degrees C/minute to 1040 degrees C for 30 minutes, etching obtained high-entropy alloy sheet using 0.3 g/mL ferric chloride hydrochloric acid aqueous solution as etching solution for 10 hours, and transferring graphene to a silica/silicon wafer.