Oxide thin films open new doors

Researchers from North Carolina State University have developed, what they claim to be, the first functional oxide thin films that can be used efficiently in electronics, opening the door to an array of new high power devices and smart sensors.

Researchers have produced positively charged (p-type) conduction and negatively charged (n-type) conduction in a single oxide material.

However, attempts to pair different p-type and n-type oxide materials previously ran into problems at the interface of the two materials - the p-n junction was always inefficient.

“We avoided this problem by using the same material for p- and n-type conduction,” said Dr Jay Narayan, the John C. Fan Distinguished Chair Prof of Materials Science and Engineering at NC State and co-author of a paper describing the research.

His team used lasers to create positively charged nickel oxide (NiO) thin films, then converted the top layer of those films to n-type. Because they could control the thickness of the n-layer, the researchers were able to control the depth and characteristics of the p-n junction.

Because oxides can handle higher voltages than silicon-based electronics, the material could be used to create higher voltage switches for the power grid, which would allow more power to be transmitted on the existing infrastructure.

Similarly, this would allow the development of sensors for use in higher temperature environments, because oxides are more stable at high temperatures. Oxide electronics could also be used to create new sensors for monitoring gases, since oxide materials can interact with oxygen.

These sensors could have a variety of applications, including testing for air toxicity in security situations.

“These materials are also transparent,” said Narayan “so this makes transparent electronics possible.”

The paper, ‘Controlled p-type to n-type conductivity transformation in NiO thin films by ultraviolet-laser irradiation,’ is published online in the Journal of Applied Physics.

The paper was co-authored by Pranav Gupta, a PhD student at NC State, Narayan and Drs Titas Dutta and Siddhartha Mal, both former PhD students at NC State, now working at Intel. The research was funded by the National Science Foundation.