Download Micky Holcomb Condensed Matter Physicist

The Physics of Faster, More
Energy-Efficient Computers
Micky Holcomb
Condensed Matter Physicist
West Virginia University
http://community.wvu.edu/~mbh039/
[email protected]
Who cares about Physics?
Why would
one study
Physics?
The Physics of Cell Phones
Finding
Signal
Power
Amplifier
Battery
Connector
Audio &
Charging
SIM Card
Connection
to Other
Devices
Power
Switch
Physics is
responsible for the
components in your
phones and
computers.
GPS &
WiFi
Runs the
Screen
Camera
Keeps Time
The internet (formally
Memory
the NSFnet*) is due to
basic science funding.
Backup
Battery
*http://en.wikipedia.org/wiki/NSFNET

Physics Helps Makes Life Better
We learn about the basic products of nature
and learn how to make some beefy devices.

Computers Have Progressed

Physics Makes Faster Computers
What is Electricity?
In some materials, these
electrons move freely
under an applied voltage.
What is a Transistor?
Time
Resistor
Transformative
Changing Variable
Resistor
http://www.youtube.com/watch?v=CkX8SkTgB0g
Improving Transistors
The number of transistors
placed inexpensively on a
computer chip has
doubled every ~2 years
(Moore’s Law)
This trend has
allowed massive
progress in
technology
1) Making Them Smaller
A voltage on the gate electrode can induce
flow of electricity between the two other
contacts called the source and drain.
Silicon
Area
Speed
Area
Electron flow
Thickness
Electron flow
The flow of electricity is affected by:
the dielectric constant of the oxide,
the area of capacitor and the oxide thickness
Quantum Tunneling?!?
Electrons
are lazy!
If the hill isn’t too wide, they tunnel through it. Not good.
2) Replacement Oxides
• High dielectric constant
• Low leakage current
• Works well with current Si technology
Many materials have been tried but none are as
cheap and easy to manipulate as existing SiO2.
3) Strain
Industry found that it could improve
electron travel in MOSFETs by straining
(essentially squeezing) silicon.
Strain can allow quicker,
more efficient transfer of
electrons.
Strain can also affect other
properties of a material.
Why We Care About Strain
Ex: roads, airplane wings, medical inserts, building materials
Reaching the Limits
1) Scaling
2) Replacements
3) Strain
We are reaching the limit that
these strategies can continue to
improve technology.

4) Different Approach: Magnetism
Magnetic
moment
electrons
Using Magnetism
0
0
1
Problems with Magnetic Fields
Magnetic
field
Require a lot of power
Heating problems
Difficult to localize – limits size
4) Different Approaches
Ferromagnetic
Ferroelectric
Spontaneous polarization
Spontaneous magnetization
whose direction can be
whose direction can be
changed with an applied
changed with an applied
Multiferroic
electric field (voltage)
magnetic field

Electrical Control of Magnetism?
Bi
Fe
P1+
Only room temperature
magnetic ferroelectric (BFO)
O
Using an electric
field to change
magnetism
P1-
Magnetic plane is
perpendicular to
the polarization
direction.
P3-
P4-

Physics at its Boundaries
- BFO is not a good candidate
- Simple idea: Grow a
magnetic material on
top of a ferroelectric
- Problem: the physics at
boundaries is not yet well
understood
Magnetoelectric Interface
Laser Molecular
Beam Epitaxy
(Laser MBE)
Programmable shutter
Chu YH, et. al., Materials
Today 10 (10), 16 (2007)
A – Magnetic layer (LSMO)
B – Ferroelectric layer (PZT)
C – Substrate
Visualizing the Nano
We study structures that are only several nanometers in length.
1 inch = 2.5 cm
= 25 million nanometers (nm)
Penny = 0.06 inches thick
(or 1,550,000 nanometers)
Human hair =
100,000 nm wide
Nanometer objects are too small to see with our eyes.
Scientists must use powerful microscopes to image objects this small.
Our “Laser”
Femtosecond pulses, one million
times smaller than nanoseconds!
Power of a laser pen:
5 mW
Power of our lab’s laser:
1500 mW
Paper will burn at 95 mW
Cooling Down the Physics
Antarctica reaches temperatures of
Cryostat
-129°F
Capable of reaching temperatures of
-450°F
This is just above ABSOLUTE ZERO,
the coldest possible temperature.
Other cool features:
Low vibration stage
Sample rotation
Measurements Elsewhere
Experiments At National Labs:
X-ray Dichroism
Photoemission Electron Microscopy (PEEM)
X-ray Production
electrons
Sample
X-rays
electrons
Collector
150 Feet
Beam of electrons forced
by magnets to go around
in circles
X-rays excite
electrons which
tell us about many
properties of the
material
Electric Control of FM
As grown
First E switch
Second E switch
Summary
Basic physics research has allowed significant progress in
computing and other modern day technologies.
As computers continue to get smaller, the physics
becomes more interesting.
Magnetic
Ferroelectric
Multiferroic materials offer a pathway to new properties/devices.
Magnetic and ferroelectric materials can be imaged and
studied at WVU and national laboratories.
Magnetic domains can be changed by an electric field.

Our Science Superheroes
A few of my collaborators:
Left to Right: Srinivas Polisetty (post-doc),
Disheng Chen (grad), Jinling Zhou (grad), Evan
Wolfe (undergrad), Micky Holcomb (advisor) and
National Chiao Tung University (Taiwan)
Charles Frye (undergrad)