Graphene Films with Large Domain Size by a Two-Step Chemical Vapor Deposition Process

Abstract

The fundamental properties of graphene are making it an attractive material for a wide variety of applications. Various techniques have been developed to produce graphene and recently we discovered the synthesis of large area graphene by chemical vapor deposition (CVD) of methane on Cu foils. We also showed that graphene growth on Cu is a surface-mediated process and the films were polycrystalline with domains having an area of tens of square micrometers. In this paper, we report on the effect of growth parameters such as temperature, and methane flow rate and partial pressure on the growth rate, domain size, and surface coverage of graphene as determined by Raman spectroscopy, and transmission and scanning electron microscopy. On the basis of the results, we developed a two-step CVD process to synthesize graphene films with domains having an area of hundreds of square micrometers. Scanning electron microscopy and Raman spectroscopy clearly show an increase in domain size by changing the growth parameters. Transmission electron microscopy further shows that the domains are crystallographically rotated with respect to each other with a range of angles from about 13 to nearly 30°. Electrical transport measurements performed on back-gated FETs show that overall films with larger domains tend to have higher carrier mobility up to about 16,000 cm(2) V(-1) s(-1) at room temperature.

How Low Nucleation Density of Graphene on CuNi Alloy is Achieved

“…The increased growth rate is attributed to the high catalytic activity of the Ni atoms for the decomposition of CH 4 molecules,5, 6 whereas the decreased graphene nucleation density on CuNi alloy has never been understood. According to the classical theory of crystal growth, a high carbon concentration should lead to a high growth rate and a high nucleation density simultaneously 7. The findings for the formation of graphene on the CuNi alloy substrate therefore appear completely contrary to the classical theory of crystal growth.…”

Structure of graphene and its disorders: a review

“…Due to the strong scattering of charge carriers, GBs can impede electronic transport, thus degrading the electrical properties (e.g. decreasing mobility and increasing resistance) of polycrystalline graphene [78,247–250]. In addition, GBs with larger grain size exhibit relatively better conductive performance [247,251].…”

“…decreasing mobility and increasing resistance) of polycrystalline graphene [78,247–250]. In addition, GBs with larger grain size exhibit relatively better conductive performance [247,251]. On the other hand, a few experiments [209,252,253] observed that the configuration of GBs or the variation of grain sizes had little effects on the conductive properties of graphene.…”

The Way towards Ultrafast Growth of Single‐Crystal Graphene on Copper

“…The growth of large‐area high‐quality graphene films is fundamental for the upcoming graphene applications. Chemical vapour deposition (CVD) method offers good prospects to produce large‐size graphene films due to its simplicity, controllability and cost‐efficiency 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75. Many researches have verified that graphene can be catalytically grown on metallic substrates, like ruthenium (Ru),13, 14 iridium (Ir),15, 16 platinum (Pt),17, 18, …”

“…Achieving a uniform monolayer graphene on Ni is still a great challenge. Especially, Cu with low carbon solubility, serving as catalytic substrate, makes the continuous uniform high‐quality monolayer graphene films accessible 31, 32, 33, 34. Nowadays, the large‐scale production and transfer of graphene film from Cu foils has been realized by the roll‐to‐roll technique 69, 70.…”