Download Electrical Control of Magnetism Boundary

Green Your Machine: The
Physics of More Efficient
Computers and Cell Phones
See the notes in the PPT file for ~script.
Micky Holcomb
Condensed Matter Physicist
West Virginia University
http://community.wvu.edu/~mbh039/
[email protected]
Progress Through Size
1950s
Shortening the Race = Faster
Doubling (Moore’s Law)
~ Every 2 years,
2
Twice>200
as many
Today,
million
transistors
canfitfitoninthe
the
transistors can
same
head ofspace
a pin!
12 years
later
With the same cost!
By 2050 - if trends continue - a device the size of a micro-SD card will
have storage of ~ 3x the brain capacity of the entire human race!
What is Electricity?
In some materials (metals),
these electrons move freely
under an applied voltage.
1) Making Them Smaller
In a transistor, a voltage on the metal can induce
flow of electricity between the two other contacts
called the source (In) and drain (Out).
In
Voltage (C)
Out
Metal
Insulator
B
A
Silicon
Area
Speed
Area
Electron flow
Thickness
Electron flow
The flow of electricity is affected by:
properties of the insulator,
the area of A&B and the insulator thickness
Quantum Tunneling?!?
Electrons
are lazy!
If the hill isn’t too wide, they tunnel through it. Not good.
2) Replacement Oxides
• Insulating properties (resists electron flow)
• “Plays nice” with current Si technology
(temperature and quality)
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 by straining (essentially
squeezing) silicon.
Strain can allow quicker,
more efficient transfer of
electrons.
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
Using Magnetism
0
0
1
Problems with Magnetic Fields
Magnetic
field
Require a lot of power
Heating problems
Difficult to localize – limits size

Electrical Control of Magnetism
Materials with strong
coupling between electricity
and magnetism at room
temperature are rare
- Simple idea: Grow a
magnetic material on
top of an electric
material
- Problem: the physics at
boundaries is not yet well
understood
Pulsed Laser Deposition (PLD)
Chamber
base
Modern growth
techniques make
fabrication of such
structures possible!
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: where the material is
-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 Absorption Spectroscopy
Photoemission Electron Microscopy (PEEM)
Electric Control of Magnetism
Before
Grey (up)
magnetic
layer
First E switch
electric layer
underneath
Average
direction
Black (right)
Arrows indicant direction of
magnetism (0 or 1)
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
Electric
Magnetoelectric materials offer a pathway to new devices.
Magnetic and ferroelectric materials can be imaged and
studied at WVU and national laboratories.
Magnetic domains can be changed by an electric field.
This work is funded by

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)