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SpinValves by
Quantum Mechanics
Thomas PrevenslikQED Radiations
Discovery Bay, Hong Kong
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
1
SpinValve ferromagnetism is based on theoretical predictions by Slonczewski and Berger a decade ago.
SpinValves comprise alternating nanoscale layers of FMs separated by a NM spacer. FM stands for ferromagnetic and
NM for non-magnetic.
Spin-polarized current is produced by passing un-polarized current through a first FM layer, the polarization unchanged as
the current flows through the NM spacer.
In the second FM layer, a giant magneto-resistance (GMR) is thought to transfer the spin angular momentum as a physical spin-torque, the process tending to produce parallel spins that
significantly lower the GMR.
Introduction
2NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
ProblemsThe significant reduction in the GMR by the alignment of
spins is not without controversy.
The relatively rigid lattice shields the spins so that any transfer of spin-torque to the second FM is unlikely.
Further, spin-torque propagates by phonons through the FM lattices, and therefore limiting spin-transfer to frequencies <
10 GHz having response times > 100 ps.
Electron spins observed to respond much faster.
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
3
Laser studies in femtomagnetism by Boeglin et al. show nanoscale FMs demagnetize on a sub-picosecond time scale
(< 350 fs) far faster than phonons can respond.
Spin transfer through the lattice therefore cannot be the mechanism for demagnetization
Bigot et al. showed about 10 ps for the lattice to thermalize prompting Bovensiepen to suggest SpinValves de-magnetize
by light noting* the dynamics are only observed while the laser field interacts with the FM
* Similarity with the EM confinement of a TIR quasi-bound state, trapped in a
potential well , but leaking to the outside world by tunneling.
Alternatives
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
4
Provided the RI of the FM is greater than that of the adjacent NM spacers, non-thermal EM radiation at EUV levels is created by the QED induced frequency up-conversion of Joule heat to the TIR confinement frequency of the FM.
RI = refractive index. EM = electromagnetic
QED = quantum electrodynamics
EUV = extreme UV, TIR total internal reflection
Excitons (holon and electron pairs) are readily created by the QED induced photoelectric effect.
Holons (positive holes) act as charge carriers that significantly reduce the GMR of the FM by a dramatic
increase in photoconductivity.
QED Induced Radiation
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
5
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
Theory
Heat Capacity of the Atom
Conservation of Energy
TIR Confinement
6
Heat Capacity of the Atom
1 10 100 10000.00001
0.0001
0.001
0.01
0.1
Thermal Wavelength - l - microns
Pla
nck
Ene
rgy
- E
- e
V
1
kT
hcexp
hc
E
7
Nanostructures
kT 0.0258 eV
Classical Physics (kT > 0)
QM(kT = 0)
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
In nanostructures, QM requires atoms to have zero heat capacity
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
Conservation of Energy
Lack of heat capacity by QM precludes Joule heat conservation in nanoelectroncs by an increase in
temperature, but how does conservation proceed?
ProposalAbsorbed EM energy is conserved by creating QED photons inside the nanostructure - by frequency up - conversion to the
TIR resonance of the nanostructure.
8
Since the RI of nanoelectroncs is greater than that of the surroundings, the QED photons are confined by TIR
corresponding to a quasi-bound state
Nanostructures ( films, wires, etc) have high surface to volume ratio, but why important?
By QM, the EM energy absorbed in the surface of nanostructures provides TIR confinement of the QED photons.
QED photons are spontaneously created by Joule heat dissipated in nanoelectronics. Simply,
f = c/ = 2nd E = hf
TIR Confinement
9NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
For a spherical NP having diameter D, = 2D
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
Electrical Response
QED Photons and Excitons
Exciton Response
Mobility
Resistance and Current
10
QED Photons and Excitons
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
d Ndt
= P
E
d N ex
dt=Y
d N P
dt=YP
E
QED Photon Rate
P = Joule heatE = QED Photon energy = Absorbed Fraction
Exciton Rate
Y = Yield of Excitons / QED Photon
11
Exciton Response
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
Where, QE and QH are number electrons and holons, V is the voltage
E and H are electron and holon mobility
d QE
dt=ηP
E−QE
μE V
L2
ElectronsdQH
dt=ηP
E−QH
μH V
L2
Holons
12
QH= L2
H V o { Y PE [1−exp (− H V o
L2 t)]+ H V o
L2 QH 0 exp (− H V o
L2 t )} For SpinValves, Ovshinsky effect , and 1/f Noise, V = Vo,
For memristors, V = Vo sin t.
∫0
𝑡
exp(− μH V o
d2 cos t) dtQH exp(− μH V o
d2 cos t )= YPE
Chen et al. expressed mobility at ambient temperature by,
where, o is the mobility at zero field F
For Alq3, = 9.22x10-3 (cm/V)1/2 .
Typically, Independent of field : o = 3.04x10-7 cm2/V-s.
Mobility
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 201313
Resistance and Current
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
R= d2 A
=d
2 A1
e ( EQE+μH Q¿¿ H) / Add2
4 e μH QH
¿
I=V oR
∨V O sin ωt
R
=1
=e (QE E+QH H )
14
= Conductivity = Resistivity
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
Applications
SpinValves
Briefly
Memristors
Ovshinsky Effect 1/f Noise
15
The QED induced switching is simulated for Alq3 film thicknesses of 10, 20, 50, and 100 nm. All films were assumed to have an initial GMR of Ro = 1x106 ohms. A voltage Vo = 1 V
was applied for 10 ns followed by Vo = -1 V for 10 ns
The QED induced reduction in GMR is significant
The 10 nm film resistance ratio R/Ro is reduced to ~ 0.000624 or (R ~ 624 ohms) in < 1 ns.
In contrast, magnetic induced GMR reductions for 125 nm Alq3 film at 100 K shows a GMR reduction of about 22%
corresponding to R/Ro = 0.78
SpinValves - Simulation
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 201316
SpinValves - Resistance
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
GMR resistance change - Write and ReadFor +1 V write and -1 V erase cycle
17
0 2 4 6 8 10 12 14 16 18 200.0001
0.001
0.01
0.1
1
Time - t - ns
Re
sist
an
ce R
atio
- R
/RO
100 nm
50 nm
20 nm10 nm
Write Erase
10 nm
Spin only Vo = + 1 V Vo = -1 V
SpinValves - Charges
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
0 2 4 6 8 10 12 14 16 18 201E+01
1E+02
1E+03
1E+04
1E+05
1E+06
1E+07
1E+08
1E+09N
um
be
r o
f H
olo
ns
- Q
H
Time - t - ns
10 nm
20 nm
50 nm
100 nm
Vo = + 1 V Vo = -1 V
Holon charges - Write and ReadFor +1 V write and -1 V erase cycle
18
The 10 nm film resistance change predicted by the QED induced photoelectric effect in GST films suggests superconductivity already exists or at least may be
approached at ambient temperature.
Superconductive nanowires are proposed* to sense single photons from an external source.
C. Soci, et al., “Nanowire Photodetectors,” J. Nanoscience and Nanotechnology, 10, 1-20, 2010
However, nanowires may be a natural QED induced superconductive interconnect in nanoelectronics.
SpinValves - Conclusions
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 201319
Memristors
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
-1.5 -1 -0.5 0 0.5 1 1.5
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
Voltage - V - Volts
Cur
rent
-
I -
Am
ps
d = 50 nm , GST mobility H = 2x10-6 cm2/V-s
20
QM creates Space Charge to change Memristor resistance ( HP claims Oxygen vacancies )
Ovshinsky Effect
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
0.1 1 10 100 1000100
1000
10000
100000
1000000
10000000
Time - t - ns
Res
ista
nce
- R
- O
hms
d = 1000 nm
d = 100 nm
d = 10 nm
Alq3 Mobility = 2x10-5 cm2/V-s, Vo = 1 V, Ro = 1 M
21
PCRAM resistance changes from QED Induced charge ( Melting is ambiguous)
1/f Noise in Nanowires
NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
G (2𝜋 𝑓 )= ∫− τ /2
τ /2
1e− jωt dt=sin ( πτ )
πf=1/ 𝑓
Step in QED Induced Charge Step in Current Step in Power
Fourier Transform of Step in Power gives 1/f Noise
/2- /2
X(t)
t
22
QM creates holons as current enters nanowire( Hooge relation based on free electrons )
By QM, submicron nanoelectronic circuit elements:
SpinValves
Memristors
Ovshinsky Devices
Nanowire Interconnects
do not increase in temperature because Joule heat is conserved by the creation of charge.
However, the QED induced charge may significantly increase the 1/f noise.
Conclusions
23NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013
Questions & Papers
Email: [email protected]
http://www.nanoqed.org
24NANOSMAT-Asia : Inter. Conf. Surf., Coat., Nano-Materials; Wuhan, CHINA, Mar. 13-15, 2013