Researchers from North
Carolina State University have developed 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. This
is 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.
To make functional electronic devices, you need materials with a p-n junction,
where the positively charged and negatively charged materials meet. 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—the p-n
junction was always inefficient.
“We avoided this problem by using the same material for p- and n-type
conduction,” says Jay Narayan, PhD, 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 create ultra high-density device features for
oxide electronics,” Narayan says.
By enabling the development of oxide electronics, the research allows for
the creation of a host of new 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
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
“These materials are also transparent,” Narayan says, “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.