The formation mechanism of hexagonal Mo₂C defects in CVD graphene grown on liquid copper

Abstract

Engineered defects in CVD graphene films are a challenge, and the growth of molybdenum carbide (Mo2C) with CVD graphene can hold great potential. The formation mechanism of Mo2C in CVD graphene is proposed.

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

“…AFM height measurement revealed that those hexagons sit on top of the graphene films, and with further elemental and thermodynamic analysis, the nature of the hexagons was identified as Mo2C. The thickness of the Mo2C hexagonal domains increased with growth time, giving heights of approximately 40, 140 and 190 nm for growth times 20, 60 and 90 min, respectively (Figure 31) [49]. Lin et al addressed the issue of the contamination on graphene's surface after the CVD process and demonstrated a design of Cu substrate architecture that leads to super-clean graphene film [203].…”

“…These observed hexagons showed no graphene characteristic peaks; therefore, AFM was used to investigate whether they are holes within the graphene film or precipitates on top of the graphene surface. AFM height measurement revealed that those hexagons sit on top of the graphene films, and with further elemental and thermodynamic analysis, the nature of the hexagons was identified as Mo 2 C. The thickness of the Mo 2 C hexagonal domains increased with growth time, giving heights of approximately 40, 140 and 190 nm for growth times 20, 60 and 90 min, respectively (Figure 31) [49]. In a previous article, AFM was utilized to study the nature of hexagonal domains on the surface of graphene film grown using APCVD on liquid Cu substrate and using Mo as the crucible material; these hexagons were absent in the case of using W as the crucible material.…”

“…Low pressure leads to an increase in the diffusion coefficient, which causes a faster graphene growth rate. Nonetheless, the issue of depositing few layers graphene in APCVD can be improved by highly diluting carbon in hydrogen [45,47,48] or increasing the growth temperature above the melting point of the growth substrate [49,50]. While the surface diffusion of reaction limits the graphene growth to a single layer upon coverage of the copper surface, it has been shown that more layers can be grown on copper [51,52].…”

“…Lui et al suggested that increasing the CVD process temperature will lead to a decrease in the substrate's surface roughness, which reduces the active sites for nucleation and improves the mobility of the active species [76]. CVD reaction temperatures close to the melting point of Cu or above (T m of Cu = 1084 • C) tend to result in high-quality graphene with monolayer, uniform, crystalline, continuous and low defects density within the graphene film, which can be due to the rapid dehydrogenation rate of the hydrocarbon feedstock and/or to the improved probability that active carbon species have on the sufficient energy needed to surmount the energy barrier and attach to the surface for the growth of the graphene film [49,50,59,75].…”

Solid Particle Erosion Behaviour and Protective Coatings for Gas Turbine Compressor Blades—A Review

“…Figure 17 shows an example of coated and uncoated compressor blades, and Table 5 lists some of the materials commonly used to form the deposited films on compressor blades. Coating processes are usually classified as one of the following three groups [137][138][139][140][141][142][143][144][145][146][147][148][149][150].…”