IBM researcher Yu-Ming Lin revealed in an interview with Custom PC that graphene can't yet fully replace silicon inside CPUs, as a graphene transistor can't be completely switched off. Perhaps future discoveries will turn the tide in graphene's favor, but as it is the material will not be able to replace the role of silicon in the digital computing regime.
Last year, IBM demonstrated a graphene transistor running at 100GHz, claiming that the technology could be used to manufacture 'zippy computer chips' in the years to come. The story, along with news that researchers at the UCLU had produced a graphene transistor with a cut-off frequency of 300GHz, prompted all sorts of predictions of silicon marching towards its demise, making way for a graphene-based future with 1THz (one terahertz, or 1,000GHz) CPUs.
However, Lin says that 'there is an important distinction between the graphene transistors that we demonstrated, and the transistors used in a CPU. Unlike silicon, 'graphene does not have an energy gap, and therefore, graphene cannot be “switched off," resulting in a small on/off ratio.'
However, he also pointed out that graphene 'may complement silicon in the form of a hybrid circuit to enrich the functionality of computer chips.' He gives the example of RF circuits, which aren't dependent on a large on/off ratio.