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We demonstrate the direct transfer of graphene from Cu foil to rigid and flexible substrates, such as glass and PET, using as an intermediate layer a thin film of polyimide (PI) mixed with an aminosilane (3-aminopropyltrimethoxysilane) or only PI, respectively. While the dry removal of graphene by an adhesive has been previously demonstrated—being removed from graphite by scotch tape or from a Cu foil by thick epoxy (~20 µm) on Si—our work is the first step towards making a substrate ready for device fabrication using the polymer-free technique. Our approach leads to an article that is transparent, thermally stable—up to 350 °C—and free of polymer residues on the device side of the graphene, which is contrary to the case of the standard wet-transfer process using PMMA. Also, in addition to previous novelty, our technique is fast and easier by using current industrial technology—a hot press and a laminator—with Cu recycling by its mechanical peel-off; it provides high interfacial stability in aqueous media and it is not restricted to a specific material—polyimide and polyamic acids can be used. All the previous reasons demonstrate a feasible process that enables device fabrication.

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Direct deposition of graphene on substrates would avoid costly, time consuming and defect inducing transfer techniques. In this paper we used ultrathin films of Ni, with thickness ranging from 5 to 50 nm, as a catalytic surface on glass to seed and promote chemical vapor deposition (CVD) of graphene. Different regimes and dynamics were studied for various parameters including temperature and reaction time. When a critical temperature (700 °C) was reached, Ni films retracted and holes formed that are open to the glass surface, where graphene deposited. After CVD, the residual Ni could be etched away and the glass substrate with graphene regained maximum transparency (>90%). The fact that we could achieve low growth temperatures indicates the potential of the technique to widen the range of substrate materials over which graphene can be directly deposited. We demonstrated this by depositing graphene patterns on ultrathin, 100 μm thick, sheet of glass with low strain point (670 °C), particularly suitable for flexible electronic and optoelectronic devices. Kodambaka, and S.-Y. Kwon, "Near room-temperature synthesis of transfer-free graphene films," Nat. Commun. 3, 645 (2012). 35. M. Kosaka, S. Takano, K. Hasegawa, and S. Noda, "Direct synthesis of few-and multi-layer graphene films on dielectric substrates by "etching-precipitation" method," Carbon 82, 254-263 (2015). 36.

A graphene (Gr) on a polyimide (PI) polymer film (Gr−PI film), obtained by a direct peel-off technique, is proposed and investigated. Thanks to its high transparency, electrical conductivity, mechanical strength, and chemical durability, the Gr−PI film is an ideal substrate for flexible electronic and optoelectronic devices, including transistors, lightemitting diodes, and plasmonic antennas. It is obtained using a straightforward method. After spin coating and curing a PI film on Gr previously grown on Cu, one can separate the Gr−PI film from the Cu foil thanks to the difference in the adhesive energy between the Gr−Cu and Gr−PI interfaces. The resulting Gr−PI film shows an average electrical sheet resistance ranging from 520 to 860 Ω/sq and a very high optical transmission (>90%), which have allowed the demonstration of a transparent heater. The surface morphology of the Gr−PI film follows that of the Cu foil, with the latter maintaining its surface properties and allowing in this way its reuse in subsequent chemical vapor deposition growth. The method can also be applied to patterned Gr, as is demonstrated for nanosize ribbons with a width of a few tens of nanometers.