MANSE Midterm Review Organic Spintronics Current team members Franklyn Burke (graduate student,...
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MANSE Midterm Review Organic Spintronics ent team members klyn Burke (graduate student, 2007-) yin Tokuc (graduate student, 2008-) . Greg Szulczewski Walton Fellow 2008-2009 n Electronics with Organic Materials”
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Transcript of MANSE Midterm Review Organic Spintronics Current team members Franklyn Burke (graduate student,...
MANSE Midterm Review
Organic Spintronics
Current team membersFranklyn Burke (graduate student, 2007-)Huesyin Tokuc (graduate student, 2008-)
Prof. Greg Szulczewski SFI Walton Fellow 2008-2009“Spin Electronics with Organic Materials”
MANSE Midterm Review
Research Acitivities
• Growth of organic microcrystals and nanowires by physical vapor deposition
• Characterization of organic wires by SEM, TEM, XRD, PL, EPR, FT-IR, and SQUID magnetometery
• Fabrication of nanogap electrodes
• Set-up high impedance probe for magnetotransport studies on crystalline organic semiconductors
• Construction of UHV chamber for spin valve growth
• Transport measurements on Alq3 based MTJs
MANSE Midterm Review
Organic Crystal GrowthAl doped 8-hydroxyquinoline
rubrene
Cu phthalocyanine (CuPc)
Physical vapor deposition
Alq3
MANSE Midterm Review
SQUID Magnetometery of Alq3
0 25 50 75 100 125 150 175 200 225 250 275 300
0.00000
0.00002
0.00004
0.00006
0.00008
0.00010
0.00012
0.00014
0.00016
0.00018
Mag
netic
mom
ent,m
-mo (
10-3A
m2)
Temperature (K)
Field -- 1TWeight -- 63.2 mg
The concentration of paramagnetic (S= ½) defect centers in Alq3 is estimated to be: 4 x10-4/formula unit.
This yield an average defect separation of ~ 11 nm.
Al-doped8-hydroxyquinolinenanowires
Unshaved materialscavenges Fe from thestainless steel die!
MANSE Midterm Review
Alignment of crystals on electrodes
Al-doped 8-hydroxquinoline rubrenea = 24.936 Å, b = 28.551 Å, c = 3.787 Å a = 14.44 Å, b = 7.18 Å, c = 26.97 Å
Nano gap
Largest μ along B axis
MANSE Midterm Review
Fabrication of nano gap electrodes
UV optical lithography to prepare Deposit Pt contacts on nanowire Hall bar by electron beam deposition
Focused–ion beam etching to produce trench
MANSE Midterm Review
Magnetotransport in organic nanowires
Al-doped 8-hydroxyquinoline
NiFe electrodes Au electrodes
Tunneling
NNH
VRH
-5 -4 -3 -2 -1 0 1 2 3 4 50
10
20
30
40
50
30K
20K
10K
4.2K
R/R
[%
]
Magnetic Field (T)
10 15 20 25 30 35 40 45 500.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
180.0
200.0
220.0
0 T
0.5 T
1 T
5 T
(k
Oh
ms.
cm)
Temperature (K)
-4 -2 0 2 40
100
200
300
400
50 K
30 K
20 K
10 K
4.2 K
(x4)
(x10)
R
/R [%
]
Magnetic Field (T)
(x2)
-4 -2 0 2 40
100
200
300
400
50 K
30 K
20 K
10 K
4.2 K
(x4)
(x10)
Magnetic Field (T)
(x2)
-4 -2 0 2 40
100
200
300
400
50 K
30 K
20 K
10 K
4.2 K
(x4)
(x10)
Magnetic Field (T)
(x2)
-4 -2 0 2 40
100
200
300
400
50 K
30 K
20 K
10 K
4.2 K
(x4)
(x10)
Magnetic Field (T)
(x2)
-4 -2 0 2 40
100
200
300
400
50 K
30 K
20 K
10 K
4.2 K
(x4)
(x10)
Magnetic Field (T)
(x2)
-4 -2 0 2 40
100
200
300
400
50 K
30 K
20 K
10 K
4.2 K
(x4)
(x10)
Magnetic Field (T)
(x2)
MANSE Midterm Review
Rubrene crystals on NiFe electrodes
-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-10 -5 0 5 10
-3
-2
-1
0
1
2
3
Cu
rre
nt
(A)
Voltage (V)
70K
70K
75K
80K
100K
150K
200K
250K
290K
Cu
rre
nt (A
)
Voltage (V)
Semiconducting behavior
σ = σo exp[-(TM/T)1/(1+d)
d =1 and TM ~ 235 K 280nm gap
MANSE Midterm Review
Magnetotransport for rubrene on NiFe
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
3.82x106
3.84x106
3.86x106
3.88x106
3.90x106
3.92x106
3.94x106
3.96x106
3.98x106
4.00x106
Res
ista
nce
()
Magnetic Field (T)
70K
1V
MR proportional to T-2.25
Negative MR scales linearly at high H
Positive MR seen at low H
No MR observed using Au electrodes
Negative MR is predicted to scale as T-1.5 for 1D VRH*
*Nguyen et al. JETP 1985, 62, 1021
300nm gap
70 K
MANSE Midterm Review
TMR characteristics of 24 x 24μm2 junctions
2.5 nm Al2O32.5 nm Al2O3/ 1nm Alq3
The MTJ Stack: SiO2/Ta(30)/CoFe(5)/Barrier/CoFe(3)/IrMn(10)/Ta(5)/Pt(5)
MANSE Midterm Review
On-going work• Metal phthalocyanine (MPc) films and crystal growth M= Mn, Fe, Co, Ni, Cu, and Zn
• Deposition of vertical spin valvesin new UHV chamber
Future work
MANSE Midterm Review
• Fabricate lateral spin valves with different coercivity electrodes and gap separation
• Vertical spin valves with crystalline MPc’s
e.g. CoFe/MgO/MPc/LiF/Co
• Magnetometery, spectroscopy, and microscopy of FM/organic and organic/FM interfaces
