Single-Crystal Graphene Films Grown More Than 100 Times as Fast as Previously Possible

Ultrafast synthesis of high-quality graphene films combined with roll-to-roll processes ushers in a new era in graphene production

2 min read
Growth of graphene on copper foils assisted by a continuous oxygen supply
Image: Peking University/Nature Nanotechnology

The adaptation of chemical vapor deposition (CVD) production of graphene so that it’s compatible with roll-to-roll processing is transforming graphene manufacturing. That effort is being led by companies like Graphene Frontiers, based in Philadelphia.

However, the production of single-crystal graphene on copper foils in a CVD process remains a fairly time consuming procedure. Fabrication of centimeter-size single crystals of graphene still takes as much as a day.

Now researchers at Hong Kong Polytechnic University and Peking University have developed a technique that accelerates the process so that the growth happens at 60 micrometers per second—far faster than the typical 0.4 µm per second. The key to this 150-fold speed increase was adding a little oxygen directly to the copper foils.

In the research, which is described in the journal Nature Nanotechnology, the China-based researchers placed an oxide substrate 15 micrometers below the copper foil. The result: a continuous supply of oxygen that lowers the energy barrier to the decomposition of the carbon feedstock, thereby increasing the graphene growth rate.

The expectations were that the oxide substrate would release the oxygen at the high temperatures inside the CVD surface (over 800 degrees Celsius). The researchers confirmed this through the use of electron spectroscopy. While the measurements indicated that oxygen was indeed being released, the amount was still fairly minimal. Nevertheless, this minuscule amount of oxygen proved sufficient for their purposes because the very small space between the oxide substrate and the copper foil created a trapping effect that multiplied the effect of the oxygen.

In their experiments, the researchers were able to successfully produce single-crystal graphene materials as large as 0.3 millimeter in just five seconds. That, according to the researchers, is more than two orders of magnitude faster than other methods in which graphene is grown on copper foils.

The researchers believe that this ultrafast synthesis of graphene makes possible a new era of scalable production of high-quality, single-crystal graphene films by combining this process with roll-to-roll methods.

Counterintuitively, speeding up the process of producing single-crystal graphene films may not automatically lead to wider adoption of graphene in various devices. Just a few years ago, graphene production was stuck at around a 25-percent utilization rate, and there is no reason to believe that demand has increased enough to have dramatically changed those figures. (Graphene producers will tell you that if demand for CVD-produced graphene suddenly spiked, volume could be doubled nearly overnight.)

Nonetheless, speed in manufacturing is always an attractive option for any product. It just might not offer a change to the graphene landscape as much as a few “killer apps” might.

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3 Ways 3D Chip Tech Is Upending Computing

AMD, Graphcore, and Intel show why the industry’s leading edge is going vertical

8 min read
A stack of 3 images.  One of a chip, another is a group of chips and a single grey chip.
Intel; Graphcore; AMD

A crop of high-performance processors is showing that the new direction for continuing Moore’s Law is all about up. Each generation of processor needs to perform better than the last, and, at its most basic, that means integrating more logic onto the silicon. But there are two problems: One is that our ability to shrink transistors and the logic and memory blocks they make up is slowing down. The other is that chips have reached their size limits. Photolithography tools can pattern only an area of about 850 square millimeters, which is about the size of a top-of-the-line Nvidia GPU.

For a few years now, developers of systems-on-chips have begun to break up their ever-larger designs into smaller chiplets and link them together inside the same package to effectively increase the silicon area, among other advantages. In CPUs, these links have mostly been so-called 2.5D, where the chiplets are set beside each other and connected using short, dense interconnects. Momentum for this type of integration will likely only grow now that most of the major manufacturers have agreed on a 2.5D chiplet-to-chiplet communications standard.

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