Researchers successfully develop single layer graphene film
Market Expertz | July 19, 2019
A research group from the Center for Multidimensional Carbon Materials (CMCM), the Institute for Basic Science (IBS), Ulsan National Institute of Science and Technology (UNIST) has developed a single layer large-area graphene film over large-area copper foils. This discovery is unique from other research conducted on single-layer graphene, as the previous studies have not been able to create an adlayer-free graphene film; those studies always involved multiple layers of graphene.
Scientists at IBS were able to refine the chemical vapor deposition (CVD) growth method by removing all carbon impurities inside the copper foils on which graphene was grown. CVD on metal foils is the most promising approach for synthesizing large-area high-quality graphene films. The team wanted to find out why adlayers of graphene appeared on the film grown on copper foils and concluded that that carbon impurities in the foil facilitate the growth and nucleation of extra layers. Dr. Da Luo, the first author of the article, explains that they found that the commercial copper foils have ‘excess carbon,’ especially near the surface, of nearly 300 nm thickness, by employing time-of-flight secondary ion mass spectrometry and combustion analysis. A technical expert from Jiangxi Copper Corporation Limited, a leading carbon foils supplier, explained to the team that the carbon is integrated into the copper foil during manufacture, possibly from hydrocarbon-based oils that are used for lubrication of rollers that are in contact with the copper foil at high rolling temperatures. The researchers removed the carbon entirely by annealing under H2 at a temperature of 1060°C, which helped them create an adlayer-free and a truly single-layer graphene film.
With the same method, the IBS researchers were also able to achieve an adlayer-free single layer and single crystal graphene film on a single crystal Cu foil. Meihui Wang, another first author, explained that with their research, they had achieved perfect uniformity in the number of layers over a large area, which will ensure a consistent device performance.