Graphene is unrivaled in its unique physical and electrical properties. It has the potential to revolutionize almost every industry, but manufacturing pristine, flat graphene is a challenge. Understanding the process that causes graphene to wrinkle will ultimately lead to higher-performance devices.
In their communication in Advanced Materials, Professor Rodney Ruoff and colleagues from the Institute for Basic Science (IBS) and Ulsan National Institute of Science and Technology (UNIST) in the Republic of Korea, demonstrate wrinkle-free graphene grown on Cu(111) foils.
Prof. Rodney Ruoff: “Our ability to make single-crystal Cu foils—actually we can make them much larger—has led to growth of large-area graphene that doesn’t have any wrinkles in it. This has many implications for future uses of graphene.”
Dr. Da Luo: “We have found epitaxial graphene grown on Cu(111) foils is free of wrinkles and under compressive strain.”
Epitaxial graphene on a Cu(111) substrate shows a much higher compressive strain than nonepitaxial graphene on polycrystalline Cu.
“The strain relaxation through the formation of wrinkles is found only in the graphene regions which are not epitaxial with the underlying Cu(111) surface.”
The G-band frequency and full width at half maximum (FWHM (G)) from the epitaxial graphene on Cu is much higher than for nonepitaxial graphene regions.
Prof. Feng Ding: “To form wrinkles in the graphene, part of the graphene has to lift off from the substrate, so the adhesion between the graphene and the substrate is very important. Also, during the formation process of the wrinkle, part of the graphene has to slide on the substrate, and therefore the friction between the wrinkled graphene and the substrate must be considered.”
DFT calculations show that a large frictional force between the graphene and the Cu(111) substrate results in a notable energy barrier that inhibits the formation of wrinkles in the epitaxial graphene.
Dr. Da Luo: “This finding may shed light on producing wrinkle-free graphene for use in electronic devices.”