3 Breakthrough in Thin Film Conductor Technology

CONTENTS: 3 Breakthrough in Thin Film Conductor Technology

Scientists from The Ohio State University, the Army Research Laboratory, and MIT have made significant advancements in developing a high-quality thin film conductor. This material is considered a promising candidate for future wearable electronics and other miniature applications due to its exceptional electron mobility and low defect density. These characteristics ensure that electrical currents can pass through the material with minimal interference, similar to a high-speed freeway with no traffic.

Patrick Taylor, a physicist at the Army Research Laboratory and the study’s lead author, likened the material’s efficiency to a car traveling swiftly on an empty highway. He emphasized that this technology’s low power consumption is crucial for both military and commercial applications. The military is particularly interested in low-power devices to extend battery life for soldiers, while the commercial sector sees this technology as a potential successor to silicon, which is nearing its performance limits.

New thin film conductor with potential applications

3 Breakthrough in Thin Film Conductor Technology: Researchers from The Ohio State University, the Army Research Laboratory, and MIT recently published their findings in Materials Today Physics regarding a high-quality thin film conductor. Co-lead author Brandi Wooten, a recent PhD graduate in materials science and engineering from Ohio State and now a research technician in mechanical and aerospace engineering, highlighted a significant milestone: the detection of elusive oscillations indicating that the pristine films are nearly scatter-free, unlike their natural counterparts.

Wooten explained that while these materials are not naturally optimal for thin film growth, the team’s research shows that they can be improved sufficiently to be used in devices. This achievement marks a significant step toward utilizing these materials in practical applications.

Furthermore, Wooten, who interned at Taylor’s lab during her PhD studies, conducted sensitive tests to evaluate the thin films’ thermal properties. The research team is already working on new versions of the films based on her findings, aiming to enhance their thermoelectric capabilities.

Although practical military and commercial applications are still years away, these energy-efficient films could be integrated with super-thin chips used in miniature electronics. Potential future applications include serving as building blocks for advanced magnetic memory in computers, generating power for robots or drones, and creating wearable devices that help keep soldiers cool while wearing heavy gear and bulletproof vests.

3 Breakthrough in Thin Film Conductor Technology: The research team has developed refined thin films, between 90 and 150 nanometers thick, based on ternary tetradymite, a mineral composed of bismuth, tellurium, and sulfur. For around two decades, scientists have been working on improving tetradymite films due to their potential as topological insulators—materials that allow electrical current to flow on the surface while the interior remains an insulator, minimizing energy dissipation. This surface conduction also possesses spin properties, which could lead to the development of spintronic devices that require very low power.

To achieve these properties, Patrick Taylor used a technique called molecular beam epitaxy (MBE) to construct the thin films, starting with the same crystal structure as tetradymite but substituting other elements to create two compositions with distinct conduction mechanisms.

Joseph Heremans, a co-lead author and professor of mechanical and aerospace engineering, materials science and engineering, and physics at Ohio State, advised Taylor on the element selection, emphasizing the importance of equilibrium in the material composition—a characteristic not typically associated with MBE-made films. This approach resulted in the films having exceptionally high electron mobility.

Brandi Wooten explained that the high electron mobility is due to the method used to grow the films, which reduces the concentration of moving charged particles found in the interior of natural tetradymites. By lowering this carrier concentration, the strong and robust surface states of the films can be utilized. In topological insulators, current can flow in one direction on the surface but not the other, preventing back-scattering and enhancing robustness.

3 Breakthrough in Thin Film Conductor Technology: This research represents a significant advancement in not only constructing these thin films but also testing their properties in the lab, as previous studies involved much larger materials.

Patrick Taylor noted that using the molecular beam epitaxy (MBE) technique opens up the possibility of integrating these materials into future computers or cell phones.

The work received support from several institutions, including the Department of Defense Basic Research Office, the Army Research Office, the National Science Foundation, the Office of Naval Research, the Canada Research Chairs Program, and the Natural Sciences and Engineering Research Council of Canada.

Additional co-authors of the study include Owen Vail, Harry Hier, and Hang Chi (now at the University of Ottawa) from the Army Research Lab, and Jagadeesh Moodera from MIT.