Large-Area Synthesis of Graphene on Palladium and Their Raman Spectroscopy

Abstract

We present a detailed investigation of the nucleation sites, growth, and morphology of large-area graphene samples synthesized via chemical vapor deposition (CVD) on bulk palladium substrates. The CVD chamber was systematically controlled over a large range of growth temperatures and durations, and the nature of graphene growth under these conditions was thoroughly investigated using a combination of scanning electron microscopy and a statistical analysis of >500 Raman spectra. Graphene growth was found to initiate at ∼825 °C, above which the growth rate increased rapidly. At T = 1000 °C, defect-free high-quality graphene was found to grow at an unprecedented rate of tens of micrometers per second, orders of magnitude faster than past reports on Cu- or Ni-based growth, thus leading to macroscopic coverage of the substrate within seconds of growth initiation. By arresting the growth at lower temperatures, we found that graphene nanoislands preferred to nucleate at very specific positions close to terrace edges and step inner edges. Evidence of both epitaxial and self-limiting growth was found. Along with monolayer graphene, both Bernal and turbostratic multilayer graphene could be obtained. A detailed evolution of the different types of graphene, as a function of both growth temperature and duration, has been presented. From these, optimal growth conditions for any chosen type of graphene sample can be inferred.

Gilding with Graphene: Rapid Chemical Vapor Deposition Synthesis of Graphene on Thin Metal Leaves

“…Carbon radicals readily dissolve into the Pd due to their lower chemical potential in bulk Pd than that on the surface as shown by molecular simulations . The synthesis mechanism is the segregation of C atoms as opposed to isothermal adsorption in the case of copper catalyst . This mechanism affords the synthesis of high‐quality monolayer graphene on nanoscale thin films by a highly dynamic recipe within a growth time t g of less than a minute.…”

“…One promising route to harness these properties for applications is to incorporate graphene on the surface or the bulk of metal structures, for example, to create composite materials . It is possible to synthesize large‐area graphene sheets on thick metal foils via CVD . Several metals can be used as catalyst material.…”

A critical review on the contributions of chemical and physical factors toward the nucleation and growth of large-area graphene

“…Pd substrates, similar to Pt, have a high carbon solubility around 4% at 1000°C. Pd is well known for its ''carbon-sponge'' ability since it allows a very high amount of carbon diffusion [97]. The lower carbon affinity of Cu compared to other metal substrates is understandable, as catalytic activity occurs due to electron transfer from the C-H bonds to the 3d orbitals of the catalyst.…”

Computational Understanding of the Growth of 2D Materials

“…In experiments, there are a variety of catalysts (e.g., Ni, [72,123,[147][148][149] Cu, [69,[73][74][75][150][151][152][153] Co, [154,155] Fe, [156] Pd, [157][158][159] Ru, [76][77][78]112,160] Rh, [68,109,161] Ir, [162][163][164] Cu-Ni alloy, [ (111) terrace. Reproduced with permission.…”