Materials in Focus
Hydrogen pressure may control graphene growth
Oak Ridge National Laboratory (ORNL). See also the press release by Ron Walli of ORNL.)
Image credit: ORNL. Click image to enlarge.
Oak Ridge National Laboratory (ORNL). See also the press release by Ron Walli of ORNL.)
Image credit: ORNL. Click image to enlarge.
Image caption: Graphene grains come in several different shapes. Hydrogen gas controls the grains' appearance.
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In one currently popular way of making graphene, methane (the carbon source) is mixed with molecular hydrogen, and the two gases flow over a copper substrate at a temperature of approximately 1000 °C. The role of hydrogen in this process has been difficult to assess because its concentration has varied from essentially zero to several thousand times the amount of methane in different experiments. Now researchers from Oak Ridge National Laboratory (ORNL) and New Mexico State University, by carefully controlling the hydrogen/methane ratio, have determined that hydrogen performs two roles in the graphene formation process: (1) it acts as a co-catalyst with the copper, and (2) it acts as an etchant to control graphene grain size and shape. The results were reported recently in ACS Nano.
