Scientists at Caltech are developing a new method for creating high-quality graphene that doesn’t require face melting temperatures for production. For those of you who follow our science news regularly, you will know that I am super excited as graphene is the next super material.
Graphene not only has a cool name but it promises to revolutionise so many aspects of science & technology, with tensile strengths that are 200 times stronger than steel and electrical conductivity that is three orders of magnitude better than our current silicon chips.
“With this new technique, we can grow large sheets of electronic-grade graphene in much less time and at much lower temperatures,” says Caltech staff scientist David Boyd, who developed the method.
Current production techniques require temperatures of 1000 degrees Celsius and only produce small quantities of the wonder material, often with useless deformations which can compromise its amazing properties.
“Previously, people were only able to grow a few square millimeters of high-mobility graphene at a time, and it required very high temperatures, long periods of time, and many steps,” says Caltech physics professor Nai-Chang Yeh, co-director of the Kavli Nanoscience Institute and the corresponding author of the new study. “Our new method can consistently produce high-mobility and nearly strain-free graphene in a single step in just a few minutes without high temperature.
“We have created sample sizes of a few square centimeters, and since we think that our method is scalable, we believe that we can grow sheets that are up to several square inches or larger, paving the way to realistic large-scale applications.”
So how did they make the breakthrough?
Well like most discoveries this has a story behind it. In 2012 Boyd was trying to reproduce a graphene manufacturing process he had read about in a journal. In this process, heated copper is used to ‘catalyse’ the growth, but as fate would have it Boyd made a mistake in the process.
Playing around with the process during his lunch break (as all good scientists do) he took a phone call which meant the copper foil was exposed to heat longer than was called for. “It was an ‘A-ha!’ moment,” Boyd says. “I realized then that the trick to growth is to have a very clean surface, one without the copper oxide.”
As Boyd recalls, he then remembered that Robert Millikan, a Nobel Prize–winning physicist and the head of Caltech from 1921 to 1945, also had to contend with removing copper oxide when he performed his famous 1916 experiment to measure Planck’s constant, which is important for calculating the amount of energy a single particle of light, or photon, contains.
The solution was to use a system first developed in the 1960s to generate a hydrogen plasma to remove the copper oxide at much lower temperatures. Boyd was stunned at how amazingly successful this technique was, but just as his earlier ‘mistake’ has led to this discovery, a pair of leaky valves was the answer to the graphene’s rapid growth.
“The valves were letting in just the right amount of methane for graphene to grow,” he says. The ability to produce graphene without the need to active heating is a game changer, “Typically, it takes about ten hours and nine to ten different steps to make a batch of high-mobility graphene using high-temperature growth methods,” Yeh says. “Our process involves one step, and it takes five minutes.”
This is a very exciting time for science and technology as if this technique can be scaled up effectively and economically, we really could change the world.
“In the future, you could have graphene-based cell-phone displays that generate their own power,” Yeh says. Another possibility, she says, is to introduce intentional imperfections into graphene’s lattice structure to create specific mechanical and electronic attributes.
“If you can strain graphene by design at the nanoscale, you can artificially engineer its properties. But for this to work, you need to start with a perfectly smooth, strain-free sheet of graphene,” Yeh says. “You can’t do this if you have a sheet of graphene that has uncontrollable defects in different places.”
Stay Curious – C.Costigan
