Researchers at the University of Minnesota Twin Cities have demonstrated an unexpected new way to change how a metal behaves electronically. By carefully engineering the atomic interactions where two materials come into contact, the team was able to significantly alter the properties of a metallic material.
The findings, published in Nature Communications, show that a phenomenon known as interfacial polarization can be used to adjust the surface work function of metallic ruthenium dioxide (RuO2) by more than 1 electron volt (eV). The effect was achieved simply by changing the thickness of an ultra-thin film by a few nanometers.
Atomic-Scale Control of Metal Properties
Polarization is typically associated with insulating materials and ferroelectrics rather than metals. However, the researchers found a way to stabilize polarization within a metallic system and use it to influence electronic behavior.
“We often think of polarization as something that belongs to insulators or ferroelectrics — not metals,” said Bharat Jalan, professor and Shell Chair in the Department of Chemical Engineering and Materials Science at the University of Minnesota. “Our work shows that, through careful interface design, you can stabilize polarization in a metallic system and use it as a knob to tune electronic properties. This opens an entirely new way of thinking about controlling metals.”
The team discovered that the effect depends strongly on the thickness of the metal layer. The most dramatic changes occurred when the ruthenium dioxide film reached approximately 4 nanometers thick, which is about the width of a single DNA strand.
A Critical Transition at 4 Nanometers
At this thickness, the metal undergoes a transition from a strained state caused by the underlying material to a more relaxed atomic arrangement. The results provide direct evidence that the way atoms are organized inside a material can have a measurable influence on its electronic characteristics.
“This was surprising,” said Seung Gyo Jeong, first author of the study and a researcher in Jalan’s group. “We expected subtle interface effects, but not such a large and controllable change in work function. Being able to visualize the polar displacements at the atomic scale and connect them directly to electronic measurements was especially exciting.”
By observing tiny atomic movements and linking them to large electronic changes, the researchers were able to show how interface engineering can be used as a powerful tool for controlling metals.
Potential Applications in Electronics and Quantum Technology
In addition to advancing scientists’ understanding of fundamental physics, the discovery could help guide the development of future electronic devices, catalytic systems, and quantum technologies.
The research involved collaborators from the University of Minnesota Twin Cities, the Massachusetts Institute of Technology, Texas A&M University, Gwangju Institute of Science and Technology, and the School of Physics at the University of Minnesota Twin Cities.
Funding for the work was provided by the U.S. Department of Energy and the Air Force Office of Scientific Research.