Improving the quality of graphene/Cu by Joule heating and enabling polymer-free direct transfer onto arbitrary substrates

Graphene grown on Cu surfaces by chemical vapour deposition is not always of the quality required for device fabrication. Here we report, a method involving Joule heating of the Cu substrate carrying graphene in ordinary vacuum so as to improve its quality. Under optimized conditions of current density (150 A/mm2) and time (15 min), there was significant improvement in the Raman features; the I2D/IG improved two to three times the value of as-obtained graphene. Additionally, extraneous growths were removed and the crystallinity improved thus enabling facile etching away of Cu without the aid of any polymer film support. The free-standing graphene transferred onto SiO2/Si substrate exhibited high field effect mobility value.

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