Work

H 2 -dependent attachment kinetics and shape evolution in chemical vapor deposition graphene growth

Year: 2017

Type: article

Abstract: Experiments on graphene growth through chemical vapor deposition (CVD) involving methane (CH 4 ) and hydrogen (H 2 ) gases reveal a complex shape evolution and a non-monotonic dependence on the partial pressure of H 2 ( p H 2 ). To explain these intriguing observations, we develop a microkinetic model for the stepwise decomposition of CH 4 into mobile radicals and consider two possible mechanisms of attachment to graphene crystals: CH radicals to hydrogen-decorated edges of the crystals and C radicals to bare crystal edges. We derive an effective mass flux and an effective kinetic coefficient, both of which depend on p H 2 , and incorporate these into a phase field model. The model reproduces both the non-monotonic dependence on p H 2 and the characteristic shapes of graphene crystals observed in experiments. At small p H 2 , growth is limited by the kinetics of attachment while at large p H 2 growth is limited because the effective mass flux is small. We also derive a simple analytical model that captures the non-monotone behavior, enables the two mechanisms of attachment to be distinguished and provides guidelines for CVD growth of defect-free 2D crystals.

Source: 2D Materials

DOI: 10.1088/2053-1583/aa74f1

Authors: Esteban Meca, Vivek B Shenoy, John Lowengrub

Institutions: University of California, Irvine, University of California System, Weierstrass Institute for Applied Analysis and Stochastics, University of Pennsylvania

Language: English

Topic: Graphene research and applications

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: bronze

Funders: National Science Foundation, Einstein Stiftung Berlin, Division of Civil, Mechanical and Manufacturing Innovation

Awards: Collaborative Research: Modeling and Simulation of the Growth of Graphene Multilayers and Heterostructures, Mechanics of Strain-Driven Nanopatterning in Alloy Systems, Collaborative Research: Modeling and Simulation of the Growth of Graphene Multilayers and Heterostructures, Collaborative Research: Modeling and Simulation of Graphene Growth