Recent research from University of Warwick has developed a new process for growing graphene with controlled imperfection that will improve performance across a range of applications - from sensors and batteries, to electronics.
Graphene is made up of a single layer of carbon atoms in a honeycomb pattern. It is the thinnest material possible, super-strong, flexible and an excellent conductor. Perfect graphene (no missing atoms or added impurities) is the strongest and most useful form, but perfection comes at a price because this perfect structure interacts weakly with other materials and lacks crucial electronic properties required in the semiconductor industry.
In a new study published in Chemical Science, a team from the University of Warwick, University of Nottingham, and Diamond Light Source has demonstrated a new way to grow graphene-like films that contain precisely engineered predictable defects, giving scientists a reproducible recipe for designing defects into graphene for specific uses.
Professor Reinhard Maurer, Department of Chemistry, University of Warwick said: "Most of the time, introducing defects into graphene is random and messy, which makes it hard to study them or use them in real devices. By carefully choosing the starting molecule and the growth conditions, we've shown it's possible to grow graphene in which imperfections appear in a highly controlled and uniform way - something that has never been achieved before."
Graphene is made up of repeating units of six carbon atoms in a ring. The desired defect has neighbouring rings consisting of 5 and 7 carbon atoms. The team used a custom-designed molecule called azupyrene that has a shape (or topology) that naturally includes the same kind of irregular rings to be introduced as defects into graphene. Azupyrene was used to grow graphene to create films with a high rate of this specific type of defect and, by changing the temperature during growth, the amount of defects in the final material could be controlled.
David A. Duncan, Associate Professor from the University of Nottingham said: "Usually defects in material are seen as problems or mistakes that reduce performance, we have used them intentionally to add functionality. We found the defects can make the graphene more "sticky" to other materials, making it more useful as a catalyst, as well as improving its capability of detecting different gasses for use in sensors. The defects can also alter the electronic and magnetic properties of the graphene, for potential applications in the semiconductor industry."
These defect-rich films were clean, free from unwanted contamination and researchers at the Graphene Institute in Manchester also successfully demonstrated that the graphene could be transferred onto different surfaces retaining the defects, a key technological achievement towards applying these films to actual devices.
This work used a wide range of advanced tools, bringing together a collaboration across the UK, Germany and Sweden using advanced microscopes at Diamond Light Source in Oxfordshire and MAX IV in Sweden, allowing the researchers to study the atomic structure of the defective graphene, demonstrating that the defects were present, and how the defects affected the chemical and electronic properties of the defective graphene.
"This study is a testament to what can be achieved through international collaboration and the integration of diverse scientific expertise," said Dr. Tien-Lin Lee from Diamond Light Source. "By combining advanced microscopy, spectroscopy, and computational modelling across institutions in the UK, Germany, and Sweden, we were able to uncover the atomic-scale mechanisms behind defect formation in graphene, something no single technique or team could have achieved alone."
