Two monolayer sheets
In the test transistor IBM reports fabricating, it achieved 10 times less noise than usual. Using two monolayer graphene sheets--one atop the other--as the channels of back-gated field-effect transistors, usable transistors with channel dimensions of 30 nanometers wide by 800 nanometers long were fabricated.
"This bilayer approach to noise reduction in graphene sheets is very effective, because the two layers do not act independently," said Lin. "Instead, the adjacent layers couple to each other with the net effect of canceling any noise picked up from the external environment."
Next, IBM wants to fully characterize the noise-cancellation effects of its bilayer architecture, as well as try it in other materials that are plagued by poor signal-to-noise ratios below 32 nanometers. The company also wants to build conventional field-effect transistors with normal overhead gates, rather than the back-gated devices it has reported on so far, which are only useful for demonstration purposes.
"For the future, we want to achieve a better understanding of why this noise-cancellation effect works the way that it does, and to see if this kind of mechanism may apply to other nanoscale materials, like nanotubes or nanowires," said Lin. "And our second direction is to try to make use of these noise-reducing properties to demonstrate a more useable devices."
Although solving this noise issue was important, IBM admits that the future of graphene as a material was not pegged to solving the noise issue. There are still several other materials-related fabrication problems that need to be solved in order to achieve reliable mass production of graphene circuitry, such as problems with homogeneity that cause poor yields of chips-per-wafer.