Micky Holcomb Condensed Matter Physicist West Virginia University
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Transcript of Micky Holcomb Condensed Matter Physicist West Virginia University
Micky HolcombCondensed Matter Physicist
West Virginia University
The Physics of Faster, More Energy-Efficient Computers
http://community.wvu.edu/~mbh039/
Who cares about Physics?
Why would one study Physics?
The Physics of Cell Phones
Physics is responsible for the components in your
phones and computers.
The internet (formally the NSFnet*) is due to basic science funding.
Memory
Battery Connector
Audio & Charging
SIM Card
Finding Signal
Power Switch
Camera
Backup Battery
GPS & WiFiPower
Amplifier Runs the Screen
Connection to Other Devices
Keeps Time
*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?
http://www.youtube.com/watch?v=CkX8SkTgB0g
ResistorTransformative
Changing Variable Resistor
Time
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
Silicon
A voltage on the gate electrode can induce flow of electricity between the two other contacts called the source and drain.
The flow of electricity is affected by: the dielectric constant of the oxide,
the area of capacitor and the oxide thickness
1) Making Them Smaller
Area Speed
Area Electron flow
Thickness Electron flow
Quantum Tunneling?!?
Electrons are lazy!
If the hill isn’t too wide, they tunnel through it. Not good.
• 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.
2) Replacement Oxides
3) StrainIndustry 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.
Ex: roads, airplane wings, medical inserts, building materials
Why We Care About Strain
Reaching the Limits
We are reaching the limit that these strategies can continue to
improve technology.
1) Scaling2) Replacements
3) Strain
0 0 1
Problems with Magnetic FieldsRequire a lot of power
Heating problemsDifficult to localize – limits
size
Magnetic field
Using Magnetism
Ferroelectric
Multiferroic
Ferromagnetic
4) Different Approaches
Spontaneous magnetization whose direction can be
changed with an applied magnetic field
Spontaneous polarization whose direction can be
changed with an applied electric field (voltage)
P1+
BiFeO
P1-
180°
P4-
109°P3-
71°
Using an electric field to change
magnetismMagnetic plane is perpendicular to the polarization
direction.
Electrical Control of Magnetism?Only room temperature
magnetic ferroelectric (BFO)
Physics at its Boundaries
Boundary- Simple idea: Grow a magnetic material on top of a ferroelectric
- BFO is not a good candidate
- Problem: the physics at boundaries is not yet well
understood
Magnetoelectric InterfaceLaser Molecular Beam Epitaxy(Laser MBE) A – Magnetic layer (LSMO)
B – Ferroelectric layer (PZT)C – Substrate
Programmable shutterChu YH, et. al., Materials Today 10 (10), 16 (2007)
SrTiO3
PbZrTiO3
LaSrMnO3
Visualizing the Nano
1 inch = 2.5 cm= 25 million nanometers (nm)
Nanometer objects are too small to see with our eyes.
We study structures that are only several nanometers in length.
Scientists must use powerful microscopes to image objects this small.
Penny = 0.06 inches thick (or 1,550,000 nanometers)
Human hair = 100,000 nm wide
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
Other cool features:Low vibration stage
Sample rotation
Measurements Elsewhere
Experiments At National Labs: X-ray Dichroism
Photoemission Electron Microscopy (PEEM)
Beam of electrons forced by magnets to go around
in circles
X-rayselectrons
Sample
Collector
X-rays excite electrons which
tell us about many properties of the
material
electrons
150 Feet
X-ray Production
As grown First E switch Second E switch
Electric Control of FM
FerroelectricMagnetic
Multiferroic materials offer a pathway to new properties/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
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: