Atom-thick interlayer enables electrical ductility of thin-film metals
High-tech, flexible, wearable electronic devices, like those used for health monitoring, could potentially save your life – as long as they work. If the device has a sudden, complete malfunction due to electrical disconnection, it becomes frustratingly unusable and at great expense.
However, new research from a team of mechanical engineers at the University of Illinois Urbana Champaign provides a readily adoptable solution: by inserting an atom-thick layer within conventional metal electrodes, the researchers were able to improve the strength and stability of electronic devices by several orders of magnitude.
The team comprises Professor SungWoo Nam’s research team: Chullhee Cho, Pilgyu Kang, Keong Yong, Jin Myung Kim, and Md Farhadul Haque; in collaboration with Professor Narayana R. Aluru’s research team, including Amir Taqieddin and Yuhang Jing. Their findings are published in Nature Electronics.
“We found that an atomically-thin layer of less than one nanometer thickness could dramatically tune mechanical and electrical behavior of a thousand times thicker metal thin-films,” said co-first author Pilgyu Kang, a former postdoctoral researcher in mechanical engineering and current professor at George Mason University. “Metal thin-films are broadly used in electrodes and interconnects, and we believe our approach could help realize higher performance in emerging areas, such as flexible solar panels integrated on curved surfaces and consumer flexible electronics.”
The team performed molecular dynamics simulations using supercomputers to support and understand the experimental observations on the increased electrical ductility.“Our simulations confirmed the experimental findings by showing that inserting a 2D material layer into the thin-metal film not only enhances the mechanical toughness of the metal film with the underlying 2D-interlayer but also leads to unique fracture propagation modes,” said Amir Taqieddin, a graduate student in mechanical engineering in the Aluru group. “The unique fracture mode results in a crack locking/delay in the metal film, and this crack locking enables the sustainability of electrical conductance of the metal-film.”
“The distinct cracking behavior we observed with the underlying 2D interlayer is caused by a spontaneously formed buckle-network, which effectively delayed the complete failure across the metal surface under deformation,” said SungWoo Nam.
The team is interested in expanding the concept to various other conducting materials as well as investigating scalability of their approach for potential impact on flexible/wearable electronics.
“Our 2D-interlayer approach is not limited to a certain combination of metals and 2D materials, which offers practical strategies to enhance the electromechanical reliability of various metal-based elements utilized in current wearable electronics applications and thus creating a positive impact to the wearable industry,” said Chullhee Cho, a graduate student in the Nam group and co-first author of the paper.
The paper, “Strain-resilient electrical functionality in thin-film metal electrodes using two-dimensional interlayers,” is available at Nature Electronics.
This research was conducted at the Materials Research Laboratory, utilizing the electron beam evaporator and the focused ion-beam instruments.
Funding was provided by the Illinois Materials Research Science and Engineering Center and other funding agencies, including NSF, NASA, AFOSR, ONR and Lawrence Livermore National Laboratory.