Designing Metal Surfaces from the Interface Up: A New Path Toward Tunable Catalysis and Electronics

MINNEAPOLIS / ST. PAUL (03/30/2026) — Researchers at the University of Minnesota Twin Cities College of Science and Engineering have discovered a new way to control the electronic behavior of a metal, by engineering atomic-scale polarization at an interface. In a study recently accepted in Nature Communications, the team shows that this approach can tune the surface work function of metallic ruthenium dioxide (RuO₂) by more than 1 eV, an exceptionally large shift for a metal, simply by adjusting film thickness at the nanometer scale.

Work function, the energy required to remove an electron from a material’s surface, is a critical parameter in electronics, catalysis, and energy technologies. Traditionally, modifying a metal’s work function requires chemical treatments, surface adsorbates, or alloying. In this work, the University of Minnesota–led team instead harnessed epitaxial strain and atomic-scale structural distortions at the interface between RuO₂ and titanium dioxide (TiO₂) to induce a hidden polarization, even within a conducting metal. Using advanced electron ptychography, the researchers directly visualized picometer-scale polar displacements at buried interfaces and linked these distortions to dramatic, thickness-controlled changes in surface work function.

“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 found that when RuO₂ films are grown under strain on TiO₂ substrates, a polarized interfacial state emerges and enhances the metal’s work function by over 1 eV, far exceeding what is typically achievable through conventional thickness effects. The effect peaks near a critical thickness of about 4 nm, where the film transitions from fully strained to relaxed, revealing a direct link between atomic structure and electronic response.

“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.”

The work also integrates theory and modeling to explain how polarization can persist, even in a metal where free electrons typically screen electric fields.

“This study challenges the long-standing assumption that polarization and metallicity are incompatible,” said Tony Low, professor of electrical and computer engineering at the University of Minnesota and co-author of the study. “Our calculations show how symmetry, strain, and interface design can allow these effects to coexist. It provides a new platform for engineering quantum and electronic materials.”

Beyond fundamental physics, the findings could impact the design of next-generation electronic, catalytic, and quantum devices. Because work function governs charge injection, chemical reactivity, and band alignment, the ability to tune it through atomic-scale interface engineering, without chemical modification, offers a versatile and scalable design strategy.

By revealing that interfacial polarization can serve as a powerful control parameter in metals, this work establishes a new frontier in oxide electronics and polar metallic systems, where structure, strain, and symmetry can be precisely orchestrated to tailor functionality from the atomic level up.

Read the full paper entitled, “Strain-Stabilized Interfacial Polarization Tunes Work Function Over 1 eV in RuO2/TiO2 Heterostructures,” on the Nature Communications website.