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Micky HolcombWest Virginia University
Bristow, Lederman, Stanescu & Wilson
Overcoming Roadblocks in Future Computing at the Center for Energy Efficient Electronics
at Marshall and WVU
http://ceee.eberly.wvu.edu/
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)
212 years
later
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!
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
A 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) Strain
Industry found that it could improve electron travel by straining—essentially
squeezing—silicon.
Strain can allow quicker, more efficient
transfer of electrons.
Stress-ApparatusWilson (Marshall)
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 Fields
Require a lot of power
Heating problems
Difficult 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
LSMO
PZT0 2 4 6 8 10 12 14
2.4
2.6
2.8
3.0
3.2
3.4
bulk model
Mn2.5+
0 2 4 6 8 10 12 142.4
2.6
2.8
3.0
3.2
3.4
bulk model interface model
Mn2.5+
0 2 4 6 8 10 12 142.4
2.6
2.8
3.0
3.2
3.4
bulk model interface model surface model
0 2 4 6 8 10 12 142.4
2.6
2.8
3.0
3.2
3.4
bulk model interface model surface model
surface and interface model
0 2 4 6 8 10 12 142.4
2.6
2.8
3.0
3.2
3.4
bulk model interface model surface model
surface and interface model Wedge type 1 Wedge type 2
LSMO thickness (nm)
Mn
vale
ncy
Mn3.3+
Zhou, Holcomb, et. al. APL, submitted
One monolayer ~ Mn2.5+ (based on data)
Magnetoelectric Interfaces
Holcomb Group
SrTiO3PbZrTiO3
LaSrMnO3
La0.7Sr0.3MnO3
0 20 40 60 80 100 1203.1
3.2
3.3
3.4
LSMO thickness~2nm~3.5nm~6nm
Val
ence
s
PZT thickness (nm)
We can control magnetization in LSMO
through thickness engineering.
LSMO PZTSTOLa0.7Sr0.3MnO3PZTSrTiO3
Aberration-Corrected STEM (Collaboration with James LeBeau, NCSU)
Combined
Individual ElementsSmooth Interfaces
Thin Topological Insulators
Glinka, Bristow, Holcomb, Lederman, APL, 2013.Simplified Setup
ElectricMagnetic Magnetoelectric and two dimensional offer a
promising pathway to new devices.
As computers continue to get smaller, the physics becomes more interesting.
These materials can be imaged and studied at WVU, Marshall and national laboratories.
Exciting information about the structure and interface has provided a deeper understanding which we hope to exploit for improved technology.
Summary
This work is funded by
