Micky HolcombCondensed Matter Physicist

West Virginia University

mikel.holcomb@mail.wvu.edu

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: