We’ve been inundated with people shrieking about the publication of a possible major breakthrough in the race to make commercial graphene. For those who have been asleep due to some kind of magic spell and missed it all, graphene is a form of carbon that is basically a gigantic, one-atom thick layer of carbon atoms in a hexagonal array. It is strong (for a one-atom thick layer, which isn’t saying much), conducts heat and electricity really well (again, for a one-atom thick layer) and is transparent and lightweight (it’s one atom thick, after all!).
The problem has been making large areas of graphene inexpensively. There are really two ways to go on this. One is, in the style of the techniques used by the two researchers awarded the 2010 Nobel Prize in physics, Geim and Novoselov, to somehow peel sheets of graphene off flakes of graphite. The other is to grow the graphene from individual atoms of carbon, using a technique like chemical vapour deposition (CVD) or plasma vapour deposition (PVD). Both are expensive, with the drawback to the graphite approach being that you make very small sheets that then need to be knitted together, and the drawback to the CVD/PVD approach being it takes an agonizingly long time, in a high vacuum system, to make this stuff and then you need to peel it off whatever it was grown on.
So imagine the furor in the press when researchers from Samsung’s Advanced Institute of Technology and Sungkyunkwan University in Suwon, South Korea, published their report in the Sciencexpress section of Science magazine, on 3 April. There was breathless debate about whether this was THE breakthrough in graphene, with the conclusions running the gamut from “who can say?” to “who knows?” with an occasional “maybe…” thrown in. My conclusion was that it was fairly obvious none of the people writing these conclusions had ponied up the $20 to read the paper.
So, I spent the $20. The title of the report is itself scary enough, “Wafer-Scale Growth of Single-Crystal Monolayer Graphene on Reusable Hydrogen-Terminated Germanium”. If that doesn’t get the blood to pumping, then nothing will. But to be serious, this actually is a breakthrough. Don’t get me wrong, the graphene made this way is still going to be expensive, but it can be made in large sheets and can be made almost defect-free.
What the teams did was to start with a silicon wafer, the same type used to make integrated circuits. They coated it uniformly with germanium, and then put a layer of hydrogen atoms over the germanium. If you grow graphene on this, their reasoning went, then the carbon atoms will bind to one another instead of the hydrogen, and should peel off the hydrogen easily. And if the hydrogen has a hole in it somewhere, the carbon won’t dissolve into the germanium metal. All good so far.
The teams placed nucleation centers on the substrate. Essentially, they put down small pieces of graphene to get the crystal to start to grow. This is already commonly done when growing graphene this way on other substrates, like silicon carbide or iridium. Then they used a low-temperature CVD process to put carbon atoms onto the surface, which formed graphene that mimicked the crystal structure of the metallic germanium underneath it, what is called epitaxial growth. Those carbon atoms came from breaking down very pure methane, CH4. But this way, a number of good things happened.
For one, the graphene didn’t stick to the hydrogen-terminated germanium substrate. The researchers could easily peel it off without having to resort to chemicals or heat. That’s very good because the substrate, which is not going to be cheap to make, is at least moderately reusable. Another good thing is that the germanium and the graphene have similar expansion and contraction with heat, so not only does the graphene grow large and uniform, it isn’t in danger of wrinkling up like on some substrates that contract more than the graphene with a change in temperature.
So this is likely a way to produce bigger sheets of graphene to work on. It won’t be cheap, owing to it being a CVD process at its core. You can only lay down a single atomic layer of carbon atoms so fast, and high vacuum systems are not free. But this is the first time big sheets of graphene have been made by any commercially-viable process.
Now, what are the implications for the resource sector? Now I get to vacillate, and say it remains to be seen. For one, we could all stop talking about how graphene is going to be great for the graphite industry. Graphene doesn’t use much carbon at all, and this type of graphene doesn’t even need graphite in any way, since everything starts with CH4. Graphite will do just fine without worrying about whether and when graphene will pull on demand, so we can relax.
The physical properties of graphene, but more importantly its price point, will tell us what the additional impact might be. Graphene is a great conductor of heat and electricity for its weight. Copper use could take a hit, but the amount of copper displaced in heat sinks and electrical conductors all comes down to the price difference between graphene and copper. Right now, to me at least, graphene still looks like it is years away, and will remain a niche material rather than become a go-to replacement for basic metals and materials. Technology exists to surprise, though, and we will definitely be hearing more about the properties of graphene after researchers get their hands on large-scale samples produced using this new technique.