On the Role of Vapor Trapping for Chemical Vapor Deposition (CVD) Grown Graphene over Copper

Abstract

The role of sample chamber configuration for the chemical vapor deposition of graphene over copper was investigated in detail. A configuration in which the gas flow is unrestricted was shown to lead to graphene with an inhomogeneous number of layers (between 1 and 3). An alternative configuration in which one end of the inner tube (in which the sample is placed) is closed so as to restrict the gas flow leads a homogeneous graphene layer number. Depending on the sample placement, either homogeneous monolayer or bilayer graphene is obtained. Under our growth conditions, the data show local conditions play a role on layer homogeneity such that under quasi-static equilibrium gas conditions not only is the layer number stabilized, but the quality of the graphene improves. In short, our data suggests vapor trapping can trap Cu species leading to higher carbon concentrations, which determines layer number and improved decomposition of the carbon feedstock (CH4), which leads to higher quality graphene.

Temperature and Copper Concentration Effects on the Formation of Graphene-Encapsulated Copper Nanoparticles from Kraft Lignin

“…In addition, the sample with a higher copper concentration had a sharp Cu 2 O peak, which was not found in that with a lower copper concentration. These indicated that a higher Cu-to-lignin weight ratio of 1:1 resulted in extra copper atoms uncovered by graphene layers and oxidized during HNO 3 purification [12]. This implies that there is an optimum Cu-to-lignin weight ratio that will cause all copper nanoparticles to be shelled by graphene layers.…”

“…The one-end-close configuration restricts the carbon gas flow and consequently generates homogeneous graphene. The placement of metal catalyst affects the concentration of trapped carbon gas and subsequently determines the number of graphene layers formed [12]. The quality of the graphene structure can also be improved by controlling the concentration of carbon sources and reducing the cooling rate during CVD synthesis [13].…”

Direct synthesis of graphene from adsorbed organic solvent molecules over copper

“…S1 in the supplementary information). 29 This final type of spectrum is associated with non-Bernal stacked or twisted bi-layer graphene with rotational angles between ca. The average size of these flakes varies between 100 nm and just over 1 µm depending on the temperature of the process (discussed later).…”

Oxidation as A Means to Remove Surface Contaminants on Cu Foil Prior to Graphene Growth by Chemical Vapor Deposition

“…2670 cm -1 which is a second order mode (of the D mode) but does not require defects for activation. 21,27,33 The positions, line shapes and relative intensities of these modes provide rich information on the graphene material such as quality, layer number etc. [34][35][36] The Raman spectra for experiment a, b and c confirm the samples are predominantly covered in monolayer graphene from the G and 2D mode positions and the relative intensity between the G and 2D.…”