NOVELTY - Sheet material comprises structures of graphene oxide and graphene, where the graphene oxide and the graphene are chemically connected to form a plane and the sheet material has a region of the graphene oxide and a region of the graphene which are divided on the plane.    USE - The sheet material is useful for producing a graphene sheet structure (all claimed), which is useful for fabricating FET, preferably complementary metal oxide semiconductor FET for solar cells.    ADVANTAGE - The sheet material is capable of simply and economically producing the graphene sheet structure with less energy consumption and without remnant surfactant thus improving carrier mobility of the FET. The FET improves mechanical property, transparency and conductivity of the solar cells.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a method of reduction of graphene oxide, comprising providing the sheet material comprising at least one atomic layer of graphene oxide and a femtosecond laser apparatus that emits a femtosecond laser shot, tuning a pulse shape and an intensity of an electric field formed by the laser shot, and emitting the laser shot onto a region of the graphene oxide sheet in a controlled manner to reduce the graphene oxide on the region;    (2) a method-1 of forming a pattern formed of graphene oxide and graphene, selecting a region of the graphene oxide sheet in a controlled manner and irradiating the region with the femtosecond laser by the reduction of graphene oxide, and forming the pattern in which the graphene oxide and the graphene coexist on the same plane;    (3) a method-2 of removing hydrogen atoms from a graphene sheet structure, comprising irradiating one of two sides of the graphene sheet structure which are hydrogen-terminated, with a femtosecond laser, while tuning the pulse shape and the intensity of the electric field for selectively removing hydrogen atoms from one of the two sides of the graphene sheet structure; and    (4) a method-3 of producing a graphene sheet structure, comprising providing a graphene sheet structure from which hydrogen atoms are removed from one of the two sides of the graphene sheet structure, and selectively attaching halogen atoms to the one side of the graphene which are no longer hydrogen-terminated for producing the graphene sheet structure having the hydrogen-terminated side and the halogen-terminated side.