In Situ Graphene Growth Dynamics on Polycrystalline Catalyst Foils

Abstract

The dynamics of graphene growth on polycrystalline Pt foils during chemical vapor deposition (CVD) are investigated using in situ scanning electron microscopy and complementary structural characterization of the catalyst with electron backscatter diffraction. A general growth model is outlined that considers precursor dissociation, mass transport, and attachment to the edge of a growing domain. We thereby analyze graphene growth dynamics at different length scales and reveal that the rate-limiting step varies throughout the process and across different regions of the catalyst surface, including different facets of an individual graphene domain. The facets that define the domain shapes lie normal to slow growth directions, which are determined by the interfacial mobility when attachment to domain edges is rate-limiting, as well as anisotropy in surface diffusion as diffusion becomes rate-limiting. Our observations and analysis thus reveal that the structure of CVD graphene films is intimately linked to that of the underlying polycrystalline catalyst, with both interfacial mobility and diffusional anisotropy depending on the presence of step edges and grain boundaries. The growth model developed serves as a general framework for understanding and optimizing the growth of 2D materials on polycrystalline catalysts.

2D Material Membranes for Operando Atmospheric Pressure Photoelectron Spectroscopy

“…Although catalytic formation of SLG was initially demonstrated on expensive single-crystalline supports prepared under ultra-high-vacuum conditions [56,57], a remarkable aspect of graphene CVD is that high-quality, continuous sheets of only a single-atom in thickness can be grown conformally over relatively rough, low-cost, polycrystalline catalyst foils [55]. This includes the rolling striations induced by the manufacturing process, topography associated with the catalysts microstructure such as grain boundaries, as well as surface roughening resulting from restructuring and sublimation at the elevated growth temperatures.…”

“…Although numerous approaches have been proposed to remove these residues, these are often accompanied by degradation of the graphene, as in the case of annealing treatments which show poor selectivity towards polymer-removal, or simply convert the polymer to amorphous carbon [77,78]. Polymer-free transfer approaches have therefore been developed that completely avoid the use of a support that covers the graphene surface [55,79,80]. Figure 3b details one such approach where rather than coating with a polymer, a support frame made from self-adhesive aluminium foil is attached around the sample edges.…”

Chemical vapour deposition of freestanding sub-60 nm graphene gyroids

“…Hence the temperature instabilities of sub-micron unit cell structures can be similarly addressed for metals that in those respects show a similar behaviour to Ni, 37 such as Co, 43 or for metals, that require higher growth temperatures but have lower self-diffusivities, such as Pt. [44][45][46] For metals, such as Cu, that require higher temperatures for graphene growth and have high self-diffusivities (3 orders of magnitude higher for Cu than Ni at 900 °C), 47,48 successfully applying our approach may be more challenging. Nonetheless there are further avenues to increase template stability for instance by plasma precoating.…”

Real time optical observation and control of atomically thin transition metal dichalcogenide synthesis

“…To analyse the intermediate products leading to the desired crystal growth, these products must be caught blindly by shutting off the furnace and quenching the synthesis by a rapid cool down. Although there are reports on real time visual observation of graphene [12][13][14] , Y2BaCuO5 and 15 vanadium dioxide nanocrystal 16 synthesis, due to the complexity of the growth process no such observations have been made for TMDCs. Figure 1 | Schematic of the CVD growth modes, custom-made CVD chamber, and an exemplary growth.…”