A highly practical route for large-area, single layer graphene from liquid carbon sources such as benzene and methanol

Through a detailed systematic study, we determined the parameters critical for high-quality, single-layer graphene formation and developed a straightforward synthesis that requires no explosive hydrogen or methane gas flow. The synthesis is further simplified by using only a liquid carbon source such as methanol. Of over a dozen liquid carbon sources studied, methanol is found to be unique in that it acts as both a carbon/hydrogen source and an inhibitor to amorphous carbon growth. No deposition of amorphous carbon was observed, regardless of vapor pressure, unlike methane and other hydrocarbons. Finally, we describe a protocol to control graphene growth to a single side or selected location on the copper substrate, which is required for most device applications. Using our novel methods, we have prepared high-quality, single-layer graphene samples at the inch scale that have been thoroughly characterized with Raman spectroscopy, optical transmittance, scanning electron microscopy and sheet resistance measurements. Our method is safe, simple, and economical and will be of value to both fundamental researchers and nanodevice engineers.