Oxidation of the polycrystalline copper–graphene nanocomposite

Abstract

Since the experimental discovery of graphene, research has progressed at an astonishing speed. This 2D honeycomb has already exhibited revolutionary electronic properties and claimed the record for strength. However, getting graphene out of the lab requires improved characterization, especially of imperfections. Hence, this paper explores one of the most important defects in a copper-graphene nanocomposite fabricated by chemical vapor deposition (CVD), which is the method most capable of producing large sheets of high-quality graphene. Through electron microscopies, optical microscopy, and Raman spectroscopy, this work details (1) the room-temperature oxidation of the copper substrate coated with graphene and (2) the heterogeneities of the graphene due to deposition and oxidation. The results indicate that this oxidation can be confined by grain boundaries, forms in the copper substrate as Cu 2 O, and minimally affects the graphene quality. This investigation also suggests that CVD can produce a variable number of high-quality, graphene layers.

Chemical Vapour Deposition of Graphene—Synthesis, Characterisation, and Applications: A Review

“…It was found that the anisotropically alignment of liquid crystal molecules with respect to graphene domain exhibit distinct birefringence nature that allow a direct way to image and identify graphene domains/grain boundaries. Moreover, simple and direct visualization of grain boundaries was demonstrated by Kunka et al, showing that it can be conducted using straightforward room temperature oxidation of CVD grown graphene on Cu substrate [ 179 ]. Graphene provides an excellent layer to protect the underlying growth metal substrate from oxidation even at elevated temperature.…”

Nanoscale characterization of the heterogeneous interfacial oxidation layer of graphene/Cu based on a SEM electron beam induced reduction effect

“…Confocal laser scanning Raman microscopy can realize identification of graphene and copper oxides with the spatial resolution of B1 mm; however, Raman microscopy is not applicable for the thin interfacial oxide layer of Gr/Cu with thickness down to a few nanometers, and it may be time intensive for mapping measurements though it offers fast characterization for single point measurement. Focused ion beam-transmission electron microscopy (FIB-TEM) and high resolution transmission electron microscopy (HRTEM) can be used to characterize the thickness and morphology of interfacial oxide layers 30,31 at nanoand even atomic-scale; however, statistically reliable information can only be acquired by imaging at multiple regions for heterogeneous interfaces.…”

Cu oxidation kinetics through graphene and its effect on the electrical properties of graphene

“…In this respect, the oxidation of Cu underlying graphene has been proposed by several researchers as a useful method to simply observe the graphene grain. [20][21][22][23][24][25][26] Because the hexagonal arrangement of carbon atoms in graphene is sufficiently compact to inhibit the penetration of oxygen (and consequently the oxidation of Cu), 27 Cu is selectively oxidized by oxidizing species, such as OH À or O À , which penetrate the G-GBs. [22][23][24] These radicals are typically dissociated from H 2 O at elevated temperatures (approximately 200 C) or under UV exposure.…”

“…Oxygens penetrating the boundary at room temperature was reported to form Cu oxide at the graphene-Cu interface. 25 Moreover, the lateral diffusion of oxygen at the graphene-Cu interface is hindered by van der Waals forces between the Cu and graphene. 26 Although the results of oxidation kinetics depend on the states of the graphene (e.g., grain size, shape, and stitching between grains) and the Cu foil (e.g., crystallographic orientation), 28 the oxidation of Cu through the grain boundary of the graphene layer has not been systematically investigated.…”