micky holcomb condensed matter physicist west virginia university

Micky HolcombCondensed Matter Physicist

West Virginia University

mikel.holcomb@mail.wvu.edu

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

Magnetic moment

electrons

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

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: