The quick and the quantum: Knezevic
applies NSF CAREER award to faster computing
peed has been one of the driving factors in the
semiconductor industry in recent years. Computers and digital devices
have progressively become faster. “For the average user, better
performance means that you can do everything you want to do faster,”
says Assistant Professor Irena
Knezevic.
Just how fast will field-effect transistors for computing
and other digital electronic applications eventually become? The very
newest and tiniest of these voltage-controlled switches can toggle between
their on and off states every picosecond, or one trillionth of a second—entering
what is called the terahertz range. “The question is, ‘Can
you go beyond this?’” says Knezevic. “Because when
transistors switch this quickly, they become very hard to characterize.”
One of five College of Engineering faculty to receive
a National
Science Foundation Faculty Early Career Development Award (CAREER)
in 2006, Knezevic will explore this question as she develops new quantum-mechanical
theory and simulators capable of describing nanoscale devices operating
on ultra-short time scales. The NSF CAREER awards, among the most prestigious
given to faculty members who are just beginning their academic careers,
are granted to creative projects that integrate research and education
effectively.
With her five-year, $400,000 award, Knezevic will
address a basic problem in the behavior of electrons, whose flow within
transistors controls the “on” and “off” states.
In transistors that switch between these states much more slowly than
once every picosecond, like those in today’s computers, electrons
act as individual entities. Thus, says Knezevic: “You can mathematically
describe transistors one electron at a time.”
But when transistors switch at time scales of a picosecond
or less, electrons begin displaying strange collective properties. Since
they don’t act individually, the familiar math no longer works.
“Now, you must treat all the electrons as one system,” she
explains, “and that requires some heavy mathematical artillery
and changes in the simulation software you use to predict electron behavior.”
Knezevic plans to develop software designed to handle
the complex algorithms needed to simulate collective electron phenomena.
This project is part of a research trend in ultrafast processes, she
says.
The software would foster quantum mechanics understanding
that applies not only to transistors, but also to any situation in which
a small system communicates with the outside world. “The issues
are general issues that occur in quantum information theory as well
as device physics,” says Knezevic. “We’ll be developing
the theory and the simulators. Notions that come out of it should be
useable not only in device simulations but more broadly.”
A major outcome of the proposed research will be
a web-based virtual nano-electronics laboratory (VNL), where graduate
students will be able to access custom-made software and supporting
materials to learn about solid state nanoelectronics and semiconductor
transport.
A big advantage of the VNL is the ability to study
nanoelectronic devices through simulation without a clean room. “The
VNL will literally allow students to play on a computer with nanodevices—to
make them, vary their features and see how they behave,” says
Knezevic.
With help from the UW-Madison Materials
Research Science and Engineering Center, she also plans to create
a version of the VNL suitable for high school students.
