arcticstoat writes: IBM has revealed that graphene can't fully replace silicon inside CPUs, as a graphene transistor can't actually be completely switched off. In an interview, Yu-Ming Lin from IBM Research — Nanometer Scale Science and Technology explained that that "graphene as it is will not replace the role of silicon in the digital computing regime." Last year, IBM demonstrated a graphene transistor running at 100GHz, while researchers at the UCLU produced a graphene transistor with a cut-off frequency of 300GHz, prompting predictions of silicon marching towards its demise, making way for a graphene-based future with 1THz 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.' That said, Lin 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.