Graphene is one of the hottest supermaterials on the horizon. It’s extraordinarily strong, flexible, thin, and light. Scientists have suspected there’s a good chance this material will upend everything from electricity generation and water filtration to computers.
But there’s a catch. Scientists have struggled in their attempts to turn graphene into a semiconductor because it’s expensive to produce, and because they haven’t been able to imbue it with the appropriate semiconductor qualities. Chiefly, that means graphene always conducts electricity. Materials scientists say it also doesn’t have a large enough bandgap, or the difference between base and excited states. Without a bandgap, electricity flows continuously. But with a bandgap, a certain amount of electricity is required before the electron jumps the gap to pass on the signal.
Now, researchers have developed a long-sought two-dimensional material that could get around some of these obstacles. It’s called graphitic carbon nitride. It is structurally comparable to graphene—a lattice in two dimensions, like a sheet—but it incorporates nitrogen. Its bandgap is large, so it can operate at higher temperatures, switch larger voltages, and allow for more impurities. Perhaps the biggest difference between graphene and carbon nitride in terms of practicality, though, lies in the way graphene is produced.
Here’s Chris Lee, writing for ArsTechnica:
To make matters more difficult, the transfer step introduces impurities. These impurities change the properties of graphene, but only locally, making the material properties uneven. On the face of it, this sounds pretty good—introducing impurities is a way of making a graphene transistor. But you want to control where the impurities end up. With this process, you can’t. So this is pretty disastrous for volume manufacturing.
Carbon nitride, by comparison, is a natural semiconductor, meaning that doping (adding impurities) may not be strictly necessary. The bandgap is large enough that a small amount of impurity introduced during processing probably won’t drastically change the electronic properties. This may allow for a more robust fabrication process compared to graphene. Furthermore, it grows on glass, so, in principle, carbon nitride devices could be fabricated on the same substrate on which it was grown. In that sense, this is quite a good step forward.
Together, graphene and carbon nitride would be a winning duo. They may not replace silicon, but someday, our computer chips and solar cells could blend the structural integrity of graphene with the benefits of a large bandgap, making processors both faster and cheaper.