Synthesis and characterization of transferable graphene by CVD method

Synthesis of large-area graphene has been realized on the top of copper substrates by chemical vapor deposition (CVD) at ambient pressure with the flow of a mixture of hydrogen and methane gases. The graphene layers were transferred to the oxidized silicon wafers employing a undercutting method. The intense G (1570 cm^-1) and 2D (2700 cm^-1) bands observed from Raman spectroscopy reveals the presence of graphene on top of oxidized silicon wafer. Reflectance spectroscopy was measured and compared with the theoretical calculation based on Fresnel´s approach estimating the thickness of the graphene layer to be 0.32 Å. The optical spectra of graphene layers could be reproduced using the complex refractive index of graphene indicating that the optical properties of graphene is not significantly different from that of in-plane graphite. As part of the device fabrication, graphene layers were tested for oxygen sensitivity in hydrogen as a function of gas composition at different temperatures.