High-frequency, scaled graphene transistors on diamond-like carbon

Diamond standard for graphene transistor Graphene, the one-atom-thick layered form of carbon, shows promise for use in high-frequency microelectronics devices. A team based at the IBM Thomas J. Watson Research Center in New York has now identified a diamond-like form of carbon, which is already well known in the semiconductor industry, as being particularly well suited for use as a substrate for graphene semiconductor devices. Graphene was grown on a copper film substrate by chemical vapour deposition (CVD) and then transferred to a wafer of diamond-like carbon. This was used to produce a high-performance graphene transistor with a cut-off frequency of 155 gigahertz at a gate length of 40 nanometres — the shortest length so far reported. This system not only achieves the highest operation speed so far for CVD-graphene transistors, but also is the smallest well-behaved transistor ever demonstrated on any graphene material. An attractive method to fabricate graphene transistors is transferring high-quality graphene sheets to a suitable substrate. This study identifies diamond-like carbon as a new substrate for graphene devices. It is attractive as few sources for scattering are expected at the interface that may lead to deterioration of device properties. Graphene transistors operating at radio frequencies with cutoff as high as 155 GHz and with scalable gate length are demonstrated. Unlike conventional semiconductor devices, the high-frequency performance of the graphene devices exhibits little temperature dependence down to 4.3 K, providing a much larger operation window than conventional devices. Owing to its high carrier mobility and saturation velocity, graphene has attracted enormous attention in recent years 1 , 2 , 3 , 4 , 5 . In particular, high-performance graphene transistors for radio-frequency (r.f.) applications are of great interest 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 . Synthesis of large-scale graphene sheets of high quality and at low cost has been demonstrated using chemical vapour deposition (CVD) methods 14 . However, very few studies have been performed on the scaling behaviour of transistors made from CVD graphene for r.f. applications, which hold great potential for commercialization. Here we report the systematic study of top-gated CVD-graphene r.f. transistors with gate lengths scaled down to 40 nm, the shortest gate length demonstrated on graphene r.f. devices. The CVD graphene was grown on copper film and transferred to a wafer of di