NOVELTY - A graphene sheet comprises: graphene comprising ten or fewer wrinkles per 1000 square micrometers of the graphene.    USE - As a graphene sheet (claimed) used in various display devices, such as a field emission display (FED), a liquid crystal display (LCD), an organic light emitting device (OLED); in a super-capacitor, a fuel cell, or a solar cell; or in a nano-device such as a field-effect transistor (FET), or a memory device, a transparent electrode, a hydrogen storage device, an optical fiber, or other electrical device.    ADVANTAGE - The graphene sheet has a large size, fewer defects, and improved quality relative to commercially available graphene. The graphene sheet has: an area of greater than or equal to 1 square millimeter; graphene coverage of greater than or equal to 99% per 1 square millimeter area of the graphene sheet; a thickness corresponding to 1-10 layers of grapheme; a thickness of 0.3-3.3 nanometers; and a three-dimensional shape. The graphene sheet having fewer wrinkles provides a more homogeneous graphene sheet having better electrical characteristics.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a graphene base comprising: either a substrate; and a graphene sheet directly on a surface of the substrate, where the graphene sheet comprises graphene and have 10 or fewer wrinkles per 1000 square millimeters of the graphene sheet; or a substrate; a first graphene sheet disposed on at least one surface of the substrate; a metal layer disposed on the first graphene sheet; and a second graphene sheet disposed on the metal layer; or a substrate having a side forming an angle with respect to a surface of the substrate; and a graphene sheet disposed on the side of the substrate; and    (2) preparing a graphene sheet, involving: forming a carbon incorporated metal layer on at least one surface of a substrate; and thermally treating the substrate and the carbon incorporated metal layer to form first and second graphene sheets on opposite surfaces of a resulting metal layer.