Grain selective Cu oxidation and anomalous shift of graphene 2D Raman peak in the graphene–Cu system

Abstract

Understanding the interaction between graphene and its supporting substrate is of paramount importance for the development of graphene based applications. In this work the interplay of the technologically relevant graphene-Cu system is investigated in detail as a function of substrate grain orientation in Cu polycrystalline foils. While (100) and (111) Cu grains show the well-known graphene-enhanced oxidation, (110) grains present a superior oxidation resistance compared to uncovered Cu and an anomalous shift of its graphene 2D Raman band which cannot be explained by the known effects of strain and doping. These results are interpreted in terms of a weak graphene-Cu coupling at the (110) grains, and show that graphene can actually be used as anticorrosion coating, contrary to previously reported. The anomalous shift is suggested to be the result of an enhanced outer Raman scattering process which surpasses the usually dominant inner process. Since Raman spectroscopy is widely used as first and main characterization tool of graphene, the existence of an anomalous shift on its 2D band not only challenges the current theory of Raman scattering in graphene, but also has profound implications from an experimental point of view.

Raman and Fluorescence Enhancement Approaches in Graphene-Based Platforms for Optical Sensing and Imaging

“…Raman phonons of graphene are also sensitive to strain, in this case, the frequencies of G and 2D peaks increase for compressive or decrease for tensile strain with a relation: Δω 2D /Δω G = 2.2 [ 96 ]. Doping and strain contributions can be separated by plotting the 2D peak position against the G peak position in a 2D-G diagram [ 97 ]. Therefore, frequency shifts of the G and 2D peaks can detect charge transfer processes occurring either related to the NPs or to the probe molecules.…”

Oxidative Originators of Graphene Barrier Coating Grown on Surfaces

“…[3,103] For example, the occurrence of inhomogeneous oxidation of the Cu surface under graphene is a common phenomenon which have been attributed to the disparate coupling between graphene and Cu faces. [104,105] Xu et al took graphene grain on different Cu facet as the system to study the Cu facet-dependent anticorrosion properties of graphene coating, and proved that the Cu facet-dependent corrosion behavior originated from the incommensurate graphene-Cu lattice alignment. [103] They prepared single-crystal graphene grains on Cu (111) and Cu(100) surfaces using the CVD method, and then Figure 9.…”

Growth and Characterization of Graphene Layers on Different Kinds of Copper Surfaces

“…This coupling not only imposes a strong compressive strain on the graphene layer due to the mismatch in the thermal expansion coefficients, but also diminishes its Raman intensity [ 15 ]. The scattering signal from the same graphene can be enhanced many times and the corresponding bands undergo redshift [ 16 ] through “decoupling” by means of, e.g., transferring the layer onto another substrate or by oxygen intercalation and oxidation processes on the copper surface [ 15 , 17 ]. It has also been reported that the rate of this oxidation and the facilitating or hindering role of graphene for this process depends on the surface crystallographic orientation of the Cu grains [ 17 ].…”