The effect of a thin gold layer on graphene: a Raman spectroscopy study

An understanding of interactions between graphene and its surroundings is crucial for application of graphene in electronic devices. Raman spectroscopy is a convenient and efficient tool to provide information about the doping, stress and defects in graphene; however application of this method is limited to the Si/SiO2 substrate which provides interference enhancement. Here we present a comprehensive Raman study of the single-layer graphene - sapphire - gold system. Due to plasmons generated in the gold-layer the Raman signal of graphene is significantly enhanced. We study the influence of the gold layer thickness and gold particle size on the enhancement. The analysis of the Raman maps showed that graphene on sapphire is only slightly doped and the spatial distribution of doping is quite homogenous. Also no significant strain was generated in graphene sandwiched by sapphire and gold.