Abstract
The high-quality graphene film can be grown on single-crystal Cu substrate by seamlessly stitching the aligned graphene domains. The roles of O2 and H2 have been intensively studied in the graphene growth kinetics, including lowering the nucleation sites and tailoring the domain structures. However, how the O2 and H2 influence Cu orientations during recrystallization prior to growing graphene, still remains unclear. Here we report that the oxidation of Cu surface tends to stabilize the Cu(001) orientation while impedes the evolution of Cu(111) single domain during annealing process. The crystal orientation-controlled synthesis of aligned graphene seeds is further realized on the long-range ordered Cu(111) substrate. With decreasing the thickness of oxide layer on Cu surface by introducing H2, the Cu(001) orientation changes into Cu(111) orientation. Meanwhile, the average domain size of Cu foils is increased from 50 μm to larger than 1000 μm. The density functional theory calculations reveal that the oxygen increases the energy barrier for Cu(111) surface and makes O/Cu(001) more stable than O/Cu(111) structure. Our work can be helpful for revealing the roles of O2 and H2 in controlling the formation of Cu single-crystal substrate as well as in growing high-quality graphene films.
Highlights
Reported to act as an etching reagent that tailors the domain structure[19,20] and terminates the graphene edges to form few layers[21,22]
In order to reveal the role of O2 in crystal orientation transition of Cu foils, the density functional theory (DFT) calculations were conducted to study the effect of O2 on the stabilities of Cu(001) and Cu(111)
During thermal treatments of Cu foils in the tube furnace, the main source of oxygen mostly can be divided into three parts: (a) the trapped air in quartz tube; (b) the native oxide layer on Cu surface; (c) the impure gas source and tiny leakages from environment
Summary
Reported to act as an etching reagent that tailors the domain structure[19,20] and terminates the graphene edges to form few layers[21,22]. The study of the roles of O2 and H2 in the crystal orientation transition of underlying substrate is a prerequisite for achieving precise control of substrate for single-crystalline graphene growth[23,24]. We designed 3 schemes to control the degree of oxidation by introducing H2 at different heat treatment stages, obtaining 3 different thicknesses of oxidation layers measured by X-ray photoelectron spectroscopy (XPS), to study how the Cu oxides affects the substrate orientation as well as grain size. After obtaining the Cu(111) single domain, the well-aligned hexagonal graphene domains showing similar orientations were grown by ambient pressure CVD(APCVD). Understanding the roles of O2 and H2 in the crystal orientation transition of Cu foil is beneficial for the growth of well-aligned graphene arrays on single domain Cu foils. This work using the roll to roll or batch to batch process can deliver scalable production of high-quality graphene films
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