Ars
Technica: Graphene is not a natural semiconductor, but it
is attractive for use in electronics because it is only one
atom thick and still lets electrons move through it. Some
devices have been made using graphene, but they tend to perform
at low levels because of current leakage. One such device is a
ring oscillator, a circuit made of an odd number of NOT gates
arranged in series, where the last gate feeds into the first,
and the output is the opposite of the input. The frequency of
the oscillations in the output can be used to measure the
effectiveness of the circuit, and previous graphene ring
oscillators have operated in the MHz frequency. A new ring
oscillator, created by an international team of researchers,
has exceeded 1.2 GHz, which lies in the ultrahigh-frequency
band used for TV broadcasting. To build the device, the team
grew the graphene parts of the circuit via
chemical
vapor deposition and varied the size of the circuit
features from 1 to 3 µm. They found that the
smallest features resulted in the highest frequency. They then
combined the oscillator with a
frequency
mixer also made from graphene. Although the device
experienced fewer voltage fluctuations than similar silicon
devices, it still suffered from current leakage and slower
speeds, which the researchers blamed on other aspects of the
setup. By fixing those things, the team expects they can make
versions of the devices that operate at hundreds of GHz, which
could find use in specialized applications.
