T.B. Limbu, F. Mendoza, R.K. Katiyar, J.J. Razink, B.R. Weiner, G. Morell
University of Puerto Rico,
Keywords: graphene, HFCVD, large grains
Summary:Hot filament chemical vapor deposition (HFCVD) is a versatile technique suitable for industrial scaling of high quality carbon nanomaterials including graphene, due mainly to its filaments which can be heated to a wide range of temperature for dissociating the precursor gas molecules. We report here the layer number controlled synthesis of high quality and large area graphene of large grain size on copper foil by using methane as the carbon precursor gas. We show that suitable combinations of different growth parameters such as substrate to filament distance, substrate heater temperature, temperature of the filaments, methane concentration, deposition time, and total gas pressure in the chamber lead to the controlled growth of monolayer, bilayer, and few-layer graphene of grain size ranging from about 5 to 17 μm. The graphene was characterized by Raman spectroscopy, optical, atomic force, and high resolution transmission electron microscopy for determination of the quality and the number of layers. The grain size of the graphene was measured by optical imaging of the selectively oxidized underlying copper foil through graphene grain boundaries via ultraviolet irradiation under moisture-rich ambient conditions. The measured sheet resistance of the graphene range from 480 to 638 Ω/□. We found that HFCVD has an advantage over conventional thermal CVD especially for high quality bilayer and few-layer graphene growth on copper.