Micky Holcomb Condensed Matter Physicist - West Virginia University

amountdollΗλεκτρονική - Συσκευές

2 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

101 εμφανίσεις

Micky
Holcomb

Condensed 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 &
WiFi

Power
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

Resistor

Trans
formative
Changing Variable
Res
istor

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 SiO
2
.




2) Replacement
Oxides

3) Strain

Industry 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) Scaling

2) Replacements

3) Strain

Magnetic
moment

electrons



4) Different Approach: Magnetism

0


0


1

Problems with Magnetic Fields

Require a lot of power

Heating problems

Difficult 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)

P
1
+

Bi

Fe

O

P
1
-

P
4
-

P
3
-

Using an electric
field to change
magnetism

Magnetic plane is
perpendicular to
the polarization
direction.



Electrical Control of Magnetism?

Only room temperature
magnetic ferroelectric (BFO)



Physics at its Boundaries

-

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 Interface

Laser Molecular
Beam
Epitaxy

(Laser MBE)

A


Magnetic
layer (LSMO)

B


Ferroelectric
layer (PZT)

C


Substrate


Programmable shutter

Chu YH,
et. al.
,
Materials
Today
10 (10), 16 (2007)

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 Physics

Antarctica 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
-
rays

electrons

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

Ferroelectric

Magnetic

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: