Direct Growth of Substrate-Adhered Graphene on Flexible Polymer Substrates for Soft Electronics

This article describes a novel method of growing graphene directly on a flexible substrate at low temperatures using plasma-enhanced chemical vapor deposition with a solid aromatic hydrocarbon source, 1,2,3,4-tetraphenylnaphthalene (TPN), which acts as the feedstock for graphene growth. TPN is embedded with copper ions that are reduced under the growth conditions to copper nanoparticles that catalyze the graphene growth and then evaporate to leave pristine graphene. Strong covalent bonds between the TPN film and the flexible substrate, prepared by depositing an aluminum oxide (Al₂O₃) layer on a colorless polyimide layer, are generated by exposing the TPN film to ultraviolet/ozone. The TPN/substrate interfacial adhesive bonds impede the sublimation of TPN from the flexible substrate at the growth temperature, and TPN can convert directly to graphene. The synthesized substrate-adhered graphene shows excellent bending stability, with small electrical resistance changes (the resistance R during bending over initial resistance R₀ was R/R₀ < 1.2 for compressive strain, and R/R₀ < 1.4 for tensile strain at ϵ = 4.68%). Graphene is appropriate for use in flexible and transparent electrodes for electronic device applications. The proposed method for directly synthesizing substrate-adhered graphene on a flexible substrate is expected to have wide applications in flexible and wearable electronics.