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Los Alamos overcomes the key obstacle to manufacturing this wonder material of the future. flexible thin-film t o u c h - pa n e l d i s p l ay s . Spray-on solar cells and extremely long-lasting batteries. Nanoelectronic computer chips and optoelectronic communications devices. Ion and gas transport membranes. Precision sensors and biosensors. All this and more, graphene can do. Graphene is made from carbon atoms arranged in flat, interconnected hexagonal rings, like chicken wire. Its simple, two-dimensional atomic structure gives it an unusual blend of electrical, mechanical, and optical properties. It is flexible and transparent. It conducts heat and electricity. It has special magnetic properties. And despite being lightweight, it is vastly stronger than steel. But its unique atomic structure is both a blessing and a curse. Because to unleash its tremendous potential, it must first be cheaply and reliably manufactured to be one atom thick and free of defects at the atomic scale. That is to say, the desirable material properties depend upon micro‑structural perfection. The trouble is, there’s no practical way to position all the carbon atoms perfectly. Graphene must be made with some sequence of macroscopic batch processes—heating and pouring and coating and dissolving and the like. The tiniest irregularity at any stage introduces performance-limiting defects into the final product. And even if researchers somehow manage to construct the graphene just so, they still must transfer it to its target substrate—whatever surface it’s supposed to reside upon, such as a thin-film display screen. Somehow, they must pick up, transport, and set down an invisible, one-atom-thick carbon sheet without altering it in any way. Enkeleda Dervishi and her team at the Los Alamos Center for Integrated Nanotechnologies have developed a process to do just that. The process starts with a sheet of copper foil, heated to 1000°C in an inert atmosphere, into which she injects methane gas, or CH 4 . The high temperature dissociates the methane into carbon and hydrogen atoms, and the carbon 16 1663 October 2017 atoms settle onto the copper foil, naturally forming hexagonal rings. At this point, however, it’s not just graphene; it’s graphene attached to copper foil. Getting the graphene off the copper and onto a target substrate, which will be used for various applications, is the tricky part. The copper can be dissolved away with an acid wash. However, to transfer the graphene onto the target substrate, a different material is required—one invulnerable to the acid but vulnerable to something else the target substrate can withstand. Two commonly used transfer materials are thermal release tape, which is sticky tape that peels away with heat, and PMMA, or “poly(methyl methacrylate),” which is a plastic that can be dissolved in acetone. Unfortunately, both materials leave a residue on the graphene surface and are too expensive and time consuming to be used at production scale (even if the residue were deemed tolerable for a particular application). Dervishi needed a better transfer medium and decided to try a plastic resin commonly known by its former trade name, Formvar. She chose Formvar because it can be produced and applied smoothly as a liquid and can be dissolved completely and easily in chloroform, without affecting the graphene. It is also durable enough to transport the graphene onto its target Image of a graphene surface from scanning probe microscopy: a probe tip scans across a graphene surface, and a computer reconstructs the positioning of its carbon atoms. On close inspection, each ring has six peaks (carbon atoms) arranged in a hexagon. CREDIT: U.S. Army Materiel Command