Spin Electronics
Download
1 / 24

Spin Electronics - PowerPoint PPT Presentation


  • 202 Views
  • Updated On :

Spin Electronics. Peng Xiong. Department of Physics and MARTECH Florida State University. QuarkNet, June 28, 2002. SOURCE. GATE. DRAIN. MOSFET. Moore’s Law… is the end in sight?. Speed: 10 0 Hz Size: 10 -2 m Cost: $10 6 /transistor. Speed: 10 9 Hz Size: 10 -7 m

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Spin Electronics' - helena


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Slide1 l.jpg

Spin Electronics

Peng Xiong

Department of Physics and MARTECH

Florida State University

QuarkNet, June 28, 2002


Slide2 l.jpg

SOURCE

GATE

DRAIN

MOSFET

Moore’s Law… is the end in sight?

Speed: 100 Hz

Size: 10-2 m

Cost: $106/transistor

  • Speed: 109 Hz

  • Size: 10-7 m

  • Cost: $10-5/transistor


Slide3 l.jpg

Magnetic Information Storage: superparamagnetic limit

  • Density: 20 Gb/in2

  • Speed: 200 Mb/s

  • Size: f2.5” x 2

  • Capacity: 50 Gb

  • Density: 2 kb/in2

  • Speed: 70 kb/s

  • Size: f24” x 50

  • Capacity: 5 Mb


Slide4 l.jpg

Superparamagnetic Limit:

thermal stability of magnetic media


Slide5 l.jpg

Semiconductor Random Access Memory: alternatives?

M

O

S

  • High speed

  • Low density

  • High power consumption

  • Volatile


Slide6 l.jpg

H

R

H

E

E

E

E

H

M

EF

EF

N(E)

N(E)

Metal-based Spintronics:

Spin valve and magnetic tunnel junction

Applications: magnetic sensors, MRAM, NV-logic


Slide7 l.jpg

GATE

Spintronics in Semiconductor: spin transistor

  • Dreams

  • High performance

  • opto-electronics

  • Single-chip computer

  • (instant on; low power)

  • Quantum computation

Datta and Das, APL, 1990

H

SOURCE

DRAIN

GaAs

  • Issues

  • Spin polarized material

  • Spin injection

  • Spin coherence

  • Spin detection

H


Slide8 l.jpg

  • Solutions:

  • Use injector with 100%

  • spin polarization

  • Non-diffusive injection

  • Conductivity matching

Spin Injection: the conductivity mismatch

I

Schmidt et.al., PRB, 2000

RN­

RF­

SC

mF­

RN¯

RF¯

mN­

mF¯

mN¯

FM


Slide9 l.jpg

E

E

CrO2: a half metal

Tc = 400 K

m = 2mB/Cr

p = 100%

Uex

E

4s

Schwarz, J. Phys. F, 1986

normal metal

half-metallic

ferromagnet

3d

metallic ferromagnet

Measurement of spin polarization: using a superconductor


Slide10 l.jpg

  • Question:

  • What could happen to an electron with energy eV < D when it hits S from N?

  • bounce back;

  • go into S as an electron;

  • C. go into S in a Cooper pair.

  • A and B

  • B and C

  • C and A

  • A and B and C

Andreev reflection: normal metal/superconductor

E

S

N

D

eV

EF

-D

N(E)

N

S


Slide11 l.jpg

Andreev reflection: normal metal/superconductor

p = 0

Z = 0

clean metallic contact

Z ~ 1

in-between

Z >> 1

tunnel junction

Blonder, Tinkham, and Klapwijk, PRB, 1982


Slide12 l.jpg

Andreev reflection: ferromagnet/superconductor

p = 75%

E

F

S

Z = 0

metallic contact

D

eV

EF

-D

Z ~ 1

in-between

DOS

Z >> 1

tunnel junction

V


Slide13 l.jpg

Comparison: normal metal and ferromagnet

p = 75%

p = 0

Z = 0

metallic contact

Z = 0

metallic contact

Z ~ 1

in-between

Z ~ 1

in-between

Z >> 1

tunnel junction

Z >> 1

tunnel junction

V

V


Slide14 l.jpg

Spin Polarization of CrO2: our approach

Planar junction  real device structure

Artificial barrier  controlled interface

Preservation of spin polarization

at and across barrier

Key step: controlled surface modification

of CrO2 via Br etch


Slide15 l.jpg

CrO2 Film Growth: Chemical Vapor Deposition

Furnace, T=280° C

O2 flow

Heater block, T=400°C

substrate

Cr8O21 precursor

Ivanov, Watts, and Lind, JAP, 2001


Slide16 l.jpg

~

V

Lock-in

dV/dI vs V in He4 (1K) or He3 (0.3K) cryostats

Junction Fabrication and Measurement

  • Grow CrO2 film

  • Pattern CrO2 stripe

  • Surface modification: Br etch

  • Deposit S cross stripes

Pb or Al

Pb or Al

I

CrO2

CrO2

TiO2


Slide17 l.jpg

Results: CrO2/(I)/Pb junctions

Metallic contact

Z = 0 p = 97%

T = 1.2 K

  • = 1.44 meV

Tunnel junction

T = 400 mK

High quality barrier

w/o inelastic scattering


Slide18 l.jpg

mH

H

Measurement of spin polarization in high-Z junctions:

using Zeeman splitting

E

D

eV

EF

-D

eV/D

N(E)

Meservey and Tedrow,

Phys. Rep., 1994

S

F


Slide19 l.jpg

Zeeman splitting in an F/I/S junction

CrO2

In order to get high Hc:

Ultrathin S film

Parallel field

Negligible s-o interaction

H

Al

Al

CrO2


Slide20 l.jpg

Results: Zeeman splitting

+2.5T

-2.5T

T =400 mK


Slide21 l.jpg

Summary (CrO2)

Verified half-metallicity of CrO2

Engineered an artificial barrier on CrO2 surface

Preserved complete spin polarization at interface

Achieved full spin injection from a half metal

Future

Apply the technique to other systems

Magnetic tunnel junction


Slide22 l.jpg

CrO2/I/Co magnetic “tunnel” junction

H

Co

CrO2

AlOx


Slide23 l.jpg

The People

Jeff Parker

Jazcek Braden

Steve Watts

Pavel Ivanov

Stephan von Molnár

Pedro Schlottmann

David Lind


Slide24 l.jpg

Let’s build

“computers with wires no wider than 100 atoms, a microscope that could view individual atoms, machines that could manipulate atoms 1 by 1, and circuits involving quantized energy levels or the interactions of quantized spins.”

Richard Feynman –

“There’s Plenty of Room at the Bottom”

1959 APS Meeting


ad