Structural properties of graphene on copper substrates

Abstract

Introduction. Studies of the substrate influence on graphene properties are relevant due to the high sensitivity of this two-dimensional material to the smallest effects. At the same time, studies dedicated to the separation of direct substrate influence and residual synthesis effects on graphene properties are not described in the literature in sufficient detail. Materials and methods. This paper presents the results of a study of the structural properties of as-grown and transferred graphene on copper substrates by Raman spectroscopy and atomic force microscopy. Results and discussion. Using Raman spectroscopy, we found that the mechanical strain in the as-grown grapheme is increased, while negligibly small in transferred graphene, the strain coefficients being of 0.22– 0.33 and ∼ 0 %, respectively. Using atomic force microscopy, we showed that this effect does not relate to the copper surface irregularities: the average roughness of the substrate surface for as-grown graphene was of 20.4 nm, while for the transferred graphene it was of 62.0 nm, the height difference being of almost an order of magnitude greater for the latter. This contradiction was explained in terms of residual synthesis effects present in case of as-grown graphene. Conclusion. Taking into account the analyzed substrate effects is important both for the refinement of methods for the initial characterization of as-grown graphene, and for practical applications requiring graphene transfer to corrugated and perforated substrates, membranes and objects of complex shape.