A University of Arkansas physicist and his colleagues have examined the
lower limits of novel materials called complex oxides and discovered that
unlike conventional semiconductors the materials not only conduct electricity,
but also develop unusual magnetic properties.
Jak Chakhalian, Jian Liu, Derek Meyers, and Benjamin Gray of the University
of Arkansas and John W. Freeland and Phillip Ryan of the Advanced Photon Source
at Argonne National Laboratory present their ideas in Physical Review
Letters.
“Contrary to what we have today in modern microelectronics devices based on
silicon, here in a single quantum well, which is just four nanometers thick, we
now have several functionalities in one device layer,” says Chakhalian,
professor of physics and holder of the Charles and Clydene Scharlau Chair in
the J. William Fulbright College of Arts and Sciences. “Engineers can use this
class of material to devise new multifunctional devices based on the electrons’
spin.”
The microelectronic materials—semiconductors—used in today’s computers, have
almost reached the lower limitation for size and functionality. Computers run
on several semiconducting devices layered together in the very smallest of
spaces, known as quantum wells, where nanoscale layers of a semiconducting
material are sandwiched between two nanoscale layers of a non-conducting
material. However, the researchers found that by using complex oxides with
correlated electrons confined to quantum well geometry, they added a new
dimension to the mix.
The new structure is based on the concept of correlated charge carriers,
like those found in rust, or iron oxide. In rust, if one electron does
something, all of the other electrons “know” about it. This phenomenon, called
correlated electrons, does not exist in silicon-based materials that run
today’s computers, televisions, and complex medical equipment; power cell
phones; and keep the electricity on in homes.
“In normal materials used today, electrons don’t care about the movement of
one another,” Chakhalian says. “We can predict their properties almost on the ‘back of an envelope’ with the help of powerful computers.” However, with
correlated materials, the calculations for the movement of one electron involve
tracking the interactions with billions of electrons, and this is beyond modern
theory capabilities.
Chakhalian and his colleagues went down to four atomic layers of a
correlated complex oxide material based on nickel and sandwiched it in between
two layers of non-conducting oxide material based on aluminum. Unlike the
semiconducting materials, the complex oxide structure revealed the unexpected
presence of both electronic and magnetic properties. These multiple properties
in a single material may allow the semiconductor industry to push the limits of
current conventional computers and develop multiple functions for a single
device, possibly allowing everyday electronics to become smaller and faster
than they are today.
Source: University of Arkansas