Researchers at Georgia Tech in the US have found that the availability of hydrogen might be the key to making graphene oxide behave well enough for use in nanoelectronics.
It turns out that for more than a month after production, graphene oxide continues to interact with hydrogen, if it is available. As a result, its structure and properties will change over the period. Understanding how and why this happens could be a step toward tweaking graphene oxide into a material suitable for making logic transistors.
"Graphene oxide is a very interesting material because its mechanical, optical and electronic properties can be controlled using thermal or chemical treatments to alter its structure," said Elisa Riedo, an associate professor in the School of Physics at the Georgia Institute of Technology.
"By controlling the properties of graphene oxide through this chemical and thermal reduction, we may arrive at a material that remains close enough to graphene in structure to maintain the order necessary for the excellent electronic properties, while having the band gap needed to create transistors," she added. "It could be that graphene oxide is the way to arrive at that type of material."
The researchers made their graphene oxide from a ten-layer stack of graphene that was grown on top of a silicon carbide wafer. They oxidised it using a mixture of sulphuric acid, sodium nitrate and potassium permanganate, and observed its structure using X-ray photoemission spectroscopy.
"We found that the material changed by itself at room temperature without any external stimulation," said Suenne Kim, a postdoctoral fellow in Riedo's laboratory. "The degree to which it was unstable at room temperature was surprising."
Over the course of the study, the team noted that the number of epoxide functional groups declined while the number of hydroxyl groups increased. The team suspected, and later confirmed experimentally, that hydrogen was involved in the changes, combining with the functional groups to form water.
Angelo Bongiorno, an assistant professor who studies computational materials chemistry in Georgia Tech's School of Chemistry and Biochemistry was drafted in to help with experiemtnal confirmation. He notes: "By understanding how to use hydrogen, we could add it or take it out, allowing us to adjust the relative distribution and concentration of the epoxide and hydroxyl species which control the properties of the material."
The work was reported in the May 6th issue of Nature Materials