Graphene oscillator circuitry reaches the Gigahertz range

Harvard

Many people think that the future of electronics is going to include graphene, a sheet of carbon just a single atom thick that allows electrons to move through as if they were massless. Some of the first electronic devices involving graphene have already been built in the lab, but graphene presents its own challenges. It's not naturally a semiconductor, and most devices based on it have had poor performance due to current leakage. Now, researchers have put together a simple graphene-based test device that can operate at over 1.2GHz, and they used it as the basis for an all-graphene frequency mixer. Although the performance still isn't good enough for real-world use, it's a major step in the right direction.

The device in question is called a ring oscillator, and it has a few uses in actual devices, but the authors of the new paper say it is "the most important class of circuits used to evaluate the performance limits of any digital technology." The Wikipedia entry on the circuits calls it the electronic equivalent of a "Hello, world!" program.

Ring oscillators work by putting an odd number of NOT gates in series, with the last one feeding back to the first as input. Because of the odd number of gates, the output will always be the opposite of the input. But the output is always slightly delayed due to the intervening circuitry. As a result of these two properties, the output will oscillate between two values, with the frequency of the oscillation becoming a measure of the circuit's performance. Graphene ring oscillators have been built, but they've only managed to perform in the Megahertz range.