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Utah, Minnesota team discover highly conductive oxide-based materials; STO/NTO offer “different road to power electronics”

Engineers from the University of Utah and the University of Minnesota have discovered that interfacing two particular oxide-based materials—strontium titanate (STO) and neodymium titanate (NTO)—makes them highly conductive, a boon for future power electronics that could result in more power-efficient laptops, electric cars and home appliances that also don’t need cumbersome power supplies. Their findings were published in an open access paper in the journal, APL Materials, from the American Institute of Physics.

The team led by University of Utah electrical and computer engineering assistant professor Berardi Sensale-Rodriguez and University of Minnesota chemical engineering and materials science assistant professor Bharat Jalan revealed that when the two oxide compounds interact with each other, the bonds between the atoms are arranged in a way that produces many free electrons—the particles that can carry electrical current. STO and NTO are by themselves known as insulators—i.e., not conductive at all. When they interface, however, the amount of electrons produced is a hundred times larger than what is possible in semiconductors.

It is also about five times more conductive than silicon [the material most used in electronics].

—Berardi Sensale-Rodriguez

1.4959284.figures.online.f3
Sheet conductivity versus electron density for various 2DEGs (2DEG = two-dimensional electron gas free to move in two dimensions, but tightly confined in the third. Most 2DEG are found in transistor-like structures made from semiconductors). The measurements show that because of an enhanced nanoscale mobility, the 2DEG in NTO/STO can reach conductivity levels that are on the same order of those in AlGaN/GaN or in typical quality large-area CVD graphene on Si-substrates. Arezoomandan et al. Click to enlarge.

This discovery could greatly improve power transistors by making power supplies much more efficient. Today, electronics manufacturers use gallium nitride for transistors in power supplies and other electronics that carry large electrical currents. GaN, however, has been optimized for many years and likely cannot be made more efficient. In this discovery made by the Utah and Minnesota team, the interface between STO and NTO can be at the very least as conductive as gallium nitride and likely will be much more in the future.

When I look at the future, I see that we can perhaps improve conductivity by an order of magnitude through optimizing of the materials growth. We are bringing the possibility of high power, low energy oxide electronics closer to reality.

—Bharat Jalan

Power transistors that use this combination of materials could lead to smaller devices and appliances because their power supplies would be more energy efficient. Because there is less power wasted (wasted electricity usually dissipates into heat), these devices will not run as hot as before, says Sensale-Rodriguez. He also believes that if more electronics use these materials for transistors, collectively it could save significant amounts of electricity for the country.

It’s fundamentally a different road toward power electronics, and the results are very exciting. But we still need to do more research.

—Berardi Sensale-Rodriguez

Co-authors on the paper also include: University of Utah electrical and computer engineering professor Ajay Nahata; U graduate students Sara Arezoomandan, Hugo Condori Quispe, Ashish Chanana; and Minnesota graduate student Peng Xu. The work at University of Minnesota is funded by the Air Force Young Investigator Research Program, and the work in Utah is primarily supported by the National Science Foundation’s Materials Research Science and Engineering Center at the University of Utah.

Resources

  • Sara Arezoomandan, Hugo Condori Quispe, Ashish Chanana, Peng Xu, Ajay Nahata, Bharat Jalan and Berardi Sensale-Rodriguez (2016) “Large nanoscale electronic conductivity in complex oxide heterostructures with ultra high electron density” APL Mater. 4, 076107 doi: 10.1063/1.4959284

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