Micky HolcombCondensed Matter Physicist
West Virginia University
Green Your Machine: The Physics of More Efficient
Computers and Cell PhonesSee the notes in the PPT file for ~script.
http://community.wvu.edu/~mbh039/
Progress Through Size1950s
Shortening the Race = Faster
~ Every 2 years,
Twice as many transistors can fit in the
same space
With the same cost!
Doubling (Moore’s Law)
2 12 yearslater
Today, >200 million transistors can fit on the
head of a pin!
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.Not in insulators.
Silicon
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).
The flow of electricity is affected by: properties of the insulator,
the area of A&B and the insulator thickness
1) Making Them Smaller
Area Speed
Area Electron flow
Thickness Electron flowA B
In OutVoltage (C)
Insulator
Metal
Quantum Tunneling?!?
Electrons are lazy!
If the hill isn’t too wide, they tunnel through it. Not good.
• 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.
2) Replacement Oxides
3) StrainIndustry found that it could improve
electron travel by straining (essentially squeezing) silicon.
Strain can allow quicker, more efficient transfer of
electrons.
Reaching the Limits
We are reaching the limit that these strategies can continue to
improve technology.
1) Scaling2) Replacements
3) Strain
4) Different Approach: Magnetism
0 0 1
Problems with Magnetic FieldsRequire a lot of power
Heating problemsDifficult to localize – limits
size
Magnetic field
Using Magnetism
Electrical Control of Magnetism
Boundary
- Simple idea: Grow a magnetic material on
top of an electric material
Materials with strong coupling between electricity
and magnetism at room temperature are rare
- Problem: the physics at boundaries is not yet well
understood
base Modern growth techniques make
fabrication of such structures possible!
Pulsed Laser Deposition (PLD)Chamber
Our “Laser”
Power of a laser pen:5 mW
Power of our lab’s laser:1500 mW
Paper will burn at 95 mW
Femtosecond pulses, one million times smaller than nanoseconds!
Cooling Down the PhysicsAntarctica reaches temperatures of
-129°F
Capable of reaching temperatures of -450°F
This is just above ABSOLUTE ZERO, the coldest possible temperature.
Cryostat: where the material is
Other cool features:Low vibration stage
Sample rotation
Measurements Elsewhere
Experiments At National Labs: X-ray Absorption Spectroscopy
Photoemission Electron Microscopy (PEEM)
Before First E switch Second E switch
Electric Control of Magnetismmagnetic
layer
Average direction
Arrows indicant direction of magnetism (0 or 1)
Grey (up)
Black (right)
electric layer underneath
ElectricMagnetic
Magnetoelectric materials offer a pathway to new devices.
As computers continue to get smaller, the physics becomes more interesting.
Basic physics research has allowed significant progress in computing and other modern day technologies.
Magnetic and ferroelectric materials can be imaged and studied at WVU and national laboratories.
Magnetic domains can be changed by an electric field.
Summary
This work is funded by
Our Science Superheroes
Left to Right: Srinivas Polisetty (post-doc), Disheng Chen (grad), Jinling Zhou (grad), Evan
Wolfe (undergrad), Micky Holcomb (advisor) and Charles Frye (undergrad) National Chiao Tung University (Taiwan)
A few of my collaborators: