Novel technique produces graphene on non-metal substrates
A team of researchers from MIT and the University of Michigan has developed a process of producing graphene, which could lead to the fabrication of the highly conductive material on a commercial scale.
Currently, most methods of making graphene first grow the material on a film of metal, such as nickel or copper, said A. John Hart, the Mitsui Career Development Associate Professor of Mechanical Engineering at MIT, and head of the research. "To make it useful, you have to get it off the metal and onto a substrate, such as a silicon wafer or a polymer sheet, or something larger like a sheet of glass," he says. "But the process of transferring it has become much more frustrating than the process of growing the graphene itself, and can damage and contaminate the graphene."
The researcher's process still uses a metal film as the template—but instead of making graphene only on top of the metal film, it makes graphene on both the film's top and bottom. The substrate in this case is silicon dioxide, a form of glass, with a film of nickel on top of it.
Hart said that using chemical vapour deposition (CVD) to deposit a graphene layer on top of the nickel film yields "not only graphene on top [of the nickel layer], but also on the bottom." The nickel film can then be peeled away, leaving just the graphene on top of the nonmetallic substrate.
This way, there's no need for a separate process to attach the graphene to the intended substrate—whether it's a large plate of glass for a display screen, or a thin, flexible material that could be used as the basis for a lightweight, portable solar cell, for example. "You do the CVD on the substrate, and, using our method, the graphene stays behind on the substrate," Hart said.
First, a nickel layer is applied to the material. Then carbon is deposited on the surface, where it forms layers of graphene above and beneath the SiO2. The top layer of graphene, attached to the nickel, easily peels away using tape, leaving behind just the lower layer of graphene stuck to the substrate. Source: MIT
In addition to the researchers at Michigan, where Hart previously taught, the work was done in collaboration with a large glass manufacturer, Guardian Industries. "To meet their manufacturing needs, it must be very scalable," Hart explained. The company currently uses a float process, where glass moves along at a speed of several meters per minute in facilities that produce hundreds of tons of glass every day.
|Related Articles||Editor's Choice|