In Situ Graphene Growth Dynamics on Polycrystalline Catalyst Foils.

Robert S Weatherup,Andrew J Pollard,Marc-Georg Willinger,Zhu-Jun Wang,Ashwin J Shahani,Stephan Hofmann,Robert Schloegl,Ken Mingard,Peter W Voorhees

doi:10.1021/acs.nanolett.6b02459

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.

Highlights

The catalytic growth of graphene and other two-dimensional (2D) materials on polycrystalline metal foils by chemical vapor deposition (CVD) has emerged as the most versatile and commercially viable technique for manufacturing continuous films to meet the industrial demand for electronicgrade material.[1,2] Remarkable in this process is that continuous single-layer graphene can be produced over large areas on low-cost polycrystalline supports[3,4] and can exhibit electronic properties comparable to those achieved by mechanical exfoliation of graphite.[5]
When growth is interface-attachment-limited, the graphene domain shape is defined by the interfacial mobility, which varies as a function of both graphene lattice orientation and the catalyst grain orientation
We investigate the growth of graphene on polycrystalline Pt foils (25 μm, 99.99%, Alfa Aesar) by CVD using in situ scanning electron microscopy (SEM)

Summary

Introduction

The catalytic growth of graphene and other two-dimensional (2D) materials on polycrystalline metal foils by chemical vapor deposition (CVD) has emerged as the most versatile and commercially viable technique for manufacturing continuous films to meet the industrial demand for electronicgrade material.[1,2] Remarkable in this process is that continuous single-layer graphene can be produced over large areas (up to several square meters) on low-cost polycrystalline supports[3,4] and can exhibit electronic properties comparable to those achieved by mechanical exfoliation of graphite.[5]. We outline a general model for growth that considers precursor dissociation, mass transport (bulk, grain boundary, and surface diffusion), and attachment to the edge of a growing domain. In this context, we analyze graphene growth dynamics at different length scales (across multiple catalyst grains, for multiple graphene domains within a grain, and for a single graphene domain) to understand the ratelimiting steps in growth and how these influence the geometry of the graphene domains that define the microstructure of the continuous graphene film. We thereby reveal that the structure of CVD graphene films formed on polycrystalline catalyst foils is intimately related to that of the underlying catalyst

Methods

Results

Conclusion