Researchers create functional oxide thin films for electronics

The development is expected to lead to an array of high-power devices and smart sensors.

According to a statement, the research marks the first time that researchers have been able to produce positively charged (p-type) conduction and negatively charged (n-type) conduction in a single oxide material, launching a new era in oxide electronics.

P-n junctions (where the positively and negatively charged materials meet) are required to make functional electronic devices. Solid-state silicon electronics achieved this decades ago, but are limited by the amount of power and temperature they can handle. Oxide materials are an attractive alternative to silicon because they can handle more power.

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

‘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 professor of materials science and engineering at NC State and co-author of a paper describing the research. ‘This is a new era in oxide electronics.’

Specifically, Narayan’s 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.

‘This spatial and temporal selectivity provides unprecedented control to “write” p-n junctions by laser beams and to create ultra-high-density device features for oxide electronics,’ Narayan said.

By enabling the development of oxide electronics, the research enables the creation of a host of technologies in a wide array of fields.

For example, 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 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.

The paper, entitled ‘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.