Graphene, along with diamond, graphite, carbon naotubes and fullerenes, is one of the crystalline forms of carbon. This material, a one-atom-thick layer of carbon, is extremely strong, nearly transparent, and an excellent conductor of heat and electricity. These properties lead scientist to naturally be drawn to it for use in the semiconductor industry. However, not enough if known about this high-performance conductor to fully take advantage of all its possibilities.
Being so efficient, graphene conducts electricity so well, to the point that the electrons are difficult to control. Control is essential if this material will ever be used to make nanoscale transistors or next-generation electronics. University of Wisconsin-Milwaukee researchers, lead by professors Lian Li and Michael Weinert, are working to resolve some of the issues. The group has identified new characteristics of electron transport in a two-dimensional sheet of graphene layered on top of a semiconductor. During their experiments, the group used the semiconductor silicon carbide. They showed that when electrons are rerouted at the interface of the graphene and its semiconductor substrate, they encounter a Schottky barrier, or energy barrier for electrons formed at a metal-semiconductor junction.
[i] If the barrier is deep enough, electrons cannot pass, unless an electric field is applied. This could lead to the possibility of turning a graphene-based device on and off. Another characteristic was also discovered that would affect the ability to ensure the current is either on or off. Intrinsic ripples form on graphene when it is placed on top of a semiconductor. These ripples are similar to the waves seen on a piece of paper that has gotten wet and then dried. “Our study says that ripples affect the barrier height and even if there’s a small variation in it, the results will be a large change in the electron transport,” says Li.[ii] These developments will help ensure electronics reliability in future graphene based products.
Currently, copper wiring is used to connect transistors in CPUs or GPUs. The International Technology Roadmap for Semiconductors (ITRS) predicts that by 2015, copper wiring will not be able to be miniaturized any further.[iii] Graphene may be the answer however. Theoretically, the material can be scaled down to just a few nanometers or less. A team of researchers from the University of California, Santa Barbara have proposed an all-graphene chip, where the transistors and interconnects are monolithically patterned on a single sheet of graphene. This possibility is particularly exciting because an all-graphene integrated circuit could surpass the current performance of the 22nm complementary metal-oxide-semiconductor devices. An all-graphene chip may become a reality by utilizing one it the materials interesting qualities: it behaves differently depending on its thickness. Narrow ribbons of graphene are semiconducting and could be used to make transistors, while wider ribbons are metallic and could be used for gates and interconnects.
While graphene’s technology possibilities seem endless, leave it to Bill Gates to think outside of the technology industry for graphene uses. The Gates Foundation has awarded $100,000 grants to 11 condom research groups, with the goal of developing a graphene-based condom.[iv] Graphene is so incredibly thin, light, and nearly impenetrable, it would make a much more enjoyable condom then the current think latex and polyurethane condoms. In reality a pure graphene condom is not possible due to its near transparency, but the National Graphene Institute at the University of Manchester, along with the other research groups, hope to create a composite material that will be more desirable then current options.
Every new experiment and every newly observed characteristic leads scientists closer to utilizing graphene’s full potential. It may even be possible to utilize graphene on a day-to-day basis in the near future. Technology discoveries and advancements would not be possible without the endless experiments and research studies.