Graphene Based Memory Device Mason Overby. Outline Memory device intro – Motivation behind...
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![Page 1: Graphene Based Memory Device Mason Overby. Outline Memory device intro – Motivation behind spintronic devices How to use graphene? GaMnAs-based device.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5518bda9550346b31f8b5427/html5/thumbnails/1.jpg)
Graphene Based Memory Device
Mason Overby
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Outline
Memory device intro– Motivation behind spintronic devices
How to use graphene? GaMnAs-based device Can we incorporate all-in-one?
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non-volatile memory devices
http://en.wikipedia.org/wiki/File:MagneticMedia.png
http://www.research.ibm.com/research/gmr.html
• “Permanent” memory state• Large writing currents required• Density of “grains”, read/write limiting factor
GMR info on IBM site
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Spintronics the solution?
Carrier spin used as two state device ( )
Able to integrate computing and memory into one device utilizing charge/spin.
GMR spin-valves
http://en.wikipedia.org/wiki/File:Spin-valve_GMR.svg
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Graphene device
-0.2 -0.1 0.0 0.1 0.2
1.910
1.915
1.920
1.925T = 4K
R (
k)
B (T)
field field
T. Shen, A. Chernyshov
2 m
Ni
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compressively strained magnetization easy axes
[100] and [010]
Properties of GaMnAs
100
010
110
101
M
I
H
φM
φH
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Properties of GaMnAs
100
010
110
101
|| || where for || , for I M I M
Large resistance anisotropy
|| m( )sin cosxy mR
m IM
transverse anisotropic magnetoresistance(TrAMR)
M
I
H
φM
φH
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Determining Magnetization Direction
010
001
M
I
H
φM
φH
001010100
010
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Use graphene as spin injector
Minimize spin scattering
GaMnAs polarizes current (1)
Polarized current change state (2)
GaMnAsGraphene
um(1)
(2)
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Limitations/difficulties
Need accurate “stamping” of graphene as conductive pads (Kim K., Nature, 475, 706 (2009)) – Lithography and plasma etch “work around”
GaMnAs Tc ~200K and below
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Room Temp Integrated Device
Short-term Ni contact pad structure Stamp grid of memory cells and evaporate Ni
contacts Potential to integrate computation and
memory devices
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Conclusion
Several methods to incorporate Graphene into memory device design
Relies on “stamping method” or etching step For Ni-contact device, need external
magnetic field Potential for GaMnAs device if Tc ~ RT