▎ 摘　　要

NOVELTY - A graphene layer comprises two-dimensional hexagonal array of carbon atoms and is free of defects. USE - Graphene layer used in electronic device, sensor, or mirror. ADVANTAGE - The graphene layer is free of defects and has thickness of less than 10 atomic layers. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (A) an electronic device and a sensor including a graphene layer which comprises two-dimensional hexagonal array of sp2-bonded carbon atoms having monocrystalline domains whose lateral dimensions are greater than 20 mu m along at least two orthogonal directions within the two-dimensional plane; (B) preparation of graphene by heating transition metal to 0.5(Tm) under vacuum and maintaining this temperature for several seconds to several minutes, exposing to hydrocarbon (preferably ethylene) gas at 1x 10-8 to 1x 10-5 torr, and cooling to 0.3-0.4(Tm) at less than or equal to 20 degrees C/minute, in which Tm is melting temperature of transition metal; and (C) a mirror comprising a substrate of fused silica form having a surface exhibiting curvature operable to focus incident beam onto a focal plane, and a graphene layer conformally adhered to the substrate to protect substrate surface from degradation due to incident beam and ambient environment.