New process could lead to more widespread use of graphene
Graphene is very thin, incredibly strong, electrically conductive and chemically inert, allowing it to be used in a wide range of technologies. It's also rather difficult to work with, however, limiting its practicality. That may be about to change, as researchers at MIT and the University of Michigan have devised a new method of large-scale graphene production.
Originally, one of the most common methods of making graphene involved quickly ripping strips of adhesive tape off of solid blocks of graphite. This resulted in one-atom-thick sheets of linked carbon atoms – graphene, in other words – being stuck to the tape in flake form.
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A more production-friendly approach involves depositing graphene on metal foil. In both cases, however, the graphene must be removed from the tape or the foil and transferred onto the substrate (such as silicon or glass) used in the particular electronic device or other application. That transfer process can be very fiddly, often resulting in the graphene being damaged or contaminated.
Using the MIT/U Michigan process, the graphene is deposited onto the final substrate as it's being produced.
In lab tests, a sheet of silicon dioxide glass (the substrate) was covered on one side with a film of nickel. Graphene was then deposited on the film via chemical vapor deposition. It formed into layers on both sides of the film, however – one layer was on the exposed top side, and one was on the underside, sandwiched between the nickel and the glass.
When the nickel film and the top layer of graphene were subsequently peeled off, the bottom layer of graphene remained behind on the glass. While the top layer could still be harvested from the foil using existing methods, the bottom layer was already in place on the glass, conceivably ready to be incorporated into a device such as a touchscreen or solar cell.
The process should work in both large- and small-scale applications, with substrates ranging from big sheets of glass to silicon microchips. According to MIT-based project leader A. John Hart, though, the uniformity and quality of the graphene still need to be improved before the technique can see wide-spread use.