UK Researchers claim to have developed a method which more than halves the temperature at which high quality graphene can be produced.
A team from Cambridge's Department of Engineering added a tiny amount of gold to the surface of a nickel film, on which graphene was then grown. The resulting allow enabled graphene to be grown at 450°C, as opposed to the 1000°C that is normally required. At the usual temperature, many of the materials that are used in common manufacturing electronics can be severely damaged so graphene can't be directly integrated into circuits. By using gold, the number of places where graphene grows on the film is reduced because the alloy blocks its growth. This means that as each graphene flake emerges it grows larger and for longer before it joins with another flake. The conductivity of the graphene is improved because electrons travelling through it are not disturbed as often by joins between flakes. The result, say the researchers, is graphene that can be produced at drastically reduced temperatures, but of the same quality that would be needed for future applications. Robert Weatherup, Hofmann Research Group, who co-led the project said: "Only once we'd developed a detailed picture of how the graphene was growing were we able to start tuning that growth and rationally engineering the catalyst – the nickel – to improve it. Understanding this is interesting from a scientific point of view, but using this knowledge to improve the growth process has been the really useful outcome of our work." According to Weatherup, specialist techniques were also employed during the process to 'sense' the atom thick layer of graphene as it grew. The researchers were able to show that graphene growth doesn't just occur when the substance cools down and that its growth isn't just affected by the surface of the catalyst film but by a region of the film underneath. "We would ideally like to produce graphene directly on to an insulating substrate, as at present the alloy has to be removed after growth for graphene to be used in applications," continued Weatherup. "The problem is that insulators tend to be less good at converting carbon containing gases into high quality graphene. Graphene growth is still a very young field, but it's moving incredibly fast. Using alloying of the catalyst, as we have here, is a brand new approach in improving the process and we expect further investigation of this will likely lead to improved graphene production, and perhaps at even lower temperatures." The findings are reported in academic journal, Nano-letters.