materials are sought. Fennie’s work has had such an impact that
he was prestigiously bestowed the so-called “genius award”
from the MacArthur Foundation. The foundation cited his
research that correctly predicted ferroelectric and ferromagnetic
characteristics of several previously unexplored metal
oxides, including that of europium titanate—a ferroelectric-ferromagnetic material synthesized by Schlom to display
electrical properties 1,000 times better than the previously best-known material of its kind.
Coincidentally, it was the same year Fennie was given the
MacArthur Award that he theorized the strontium titanium
oxide for Schlom. It was at that point Schlom used a method
known as molecular-beam epitaxy to stack atomic layers of the
material according to Fennie’s blueprint. The new material was
synthesized with layers of strontium titanate separated by a
mono-layer of strontium oxide. The interface of these layers is
what gives the material its ability to record high frequencies,
enabling cellphones to have greater bandwidth, less interference
and fewer dropped calls.
“It is clear that we have discovered a killer material,”
Schlom told the Cornell Chronicle after the study was first
published, “but it is likely that even better tunable dielectrics
can be found using our approach.”
Not every university can take that approach, however,
because not every university has access to molecular-beam
epitaxy or facilities for characterization. PARADIM’s aim is
to change that, empowering engineers with a platform to
theorize, synthesis and characterize a material. That theory-
to-characterization cycle is what Schlom and colleagues have
been doing with great success, and now they’re changing the
paradigm for others.
David Muller, professor of applied and engineering physics, points to an image from an electron microscope.
hile some Cornell engineers are focused on new
materials, others are thinking about established
materials in new ways.
Gallium nitride—a semiconductor with a wide
energy bandgap—has been a recent focus of the electronics
community, and for a good reason. When considering options
for a material that could improve electronics beyond what
silicon can offer, gallium nitride fits the bill. Its properties allow
it to operate quickly within a circuit, accommodating relatively
large amounts of electricity and operating at high temperatures.
“The challenge with silicon-based electronics is that if you
want to support a reasonably large voltage, the entire circuit
has to be slow, which means you have to use large, passive
capacitors and inductors,” said Huili Grace Xing, the Richard
Lunquist Sesquicentennial Professor of Electrical and Computer
Engineering, and of materials science and engineering.
And it’s not just consumer electronics such as cellphones
and computers that could benefit from gallium nitride’s unique
properties. Dwindling fossil fuels along with climate change
have intensified efforts to improve alternative energy devices
such as electric motors, smart grids and solar cells—all devices
where the inefficiency of silicon has left room for improvement.
But gallium nitride has a tendency for defects that, for
some applications, make it unreliable. Xing has been working
to improve the semiconductor’s properties, and in 2015, she
and Debdeep Jena, also a professor within the same two
departments, published a study demonstrating a gallium
nitride power diode—a circuit component used to regulate the
flow of electricity.