Scientists Discover Way to Control Metallic Electronic Properties via Nanometre Thickness
A research team from the University of Minnesota Twin Cities has successfully demonstrated a surprising new way to alter the electronic behaviour of a metal. By carefully designing atomic interactions at the junction of two materials, the team was able to significantly change the properties of the metallic material.
The research, published in the journal Nature Communications, shows that a phenomenon known as interface polarisation can be used to regulate the surface work function of ruthenium dioxide (RuO2) by more than 1 electron volt (eV). This remarkable effect was achieved simply by altering the thickness of the ultra-thin film layer by only a few nanometres.
Generally, polarisation is associated with insulating and ferroelectric materials, rather than metallic materials. However, the researchers found a unique way to stabilise polarisation within a metallic system and use it to influence electronic behaviour.
“We often think that polarisation is something possessed by insulators or ferroelectries, not metals,” said Bharat Jalan, professor and Shell Chair in the Department of Chemical Engineering and Materials Science at the University of Minnesota. “Our science shows that, through careful interface design, you can stabilise polarisation in a metallic system and use it as a switch to regulate electronic properties. This opens up an entirely new way of thinking about controlling metals.”
The research team found that this change effect is highly dependent on the thickness of the metal layer. The most dramatic changes occur when the ruthenium dioxide layer reaches a thickness of approximately 4 nanometres, which is equivalent to the width of a single strand of human DNA.
At this 4-nanometre thickness, the metal undergoes a phase transition from a strained state, due to the influence of the underlying material, to a more relaxed atomic arrangement. This result provides direct evidence that the way atoms are arranged within a material can exert a measurable influence on its electronic characteristics.
“It is very surprising,” said Seung Gyo Jeong, the study’s lead author and a researcher in Professor Jalan’s group. “We anticipated a subtle interface effect, but we did not expect such a large and controllable change in the work function. Being able to visualise the polar shift at the atomic scale and link it directly to electronic measurements is incredibly exciting.”
The success in monitoring micro-sized atomic movements that are directly linked to large-scale electronic changes proves that interface engineering can serve as a powerful new tool for controlling metals. Beyond expanding the fundamental understanding of scientists in the field of physics, this discovery is expected to guide the development of future electronic devices, catalysis systems, and quantum technology.