수송특성측정방법physics.snu.ac.kr/nml/2008summerschool/lecture/jungmh.pdf · 2008. 7....
TRANSCRIPT
![Page 1: 수송특성측정방법physics.snu.ac.kr/nml/2008summerschool/lecture/JungMH.pdf · 2008. 7. 9. · Magnetic Property Measurement System 2008.12. System performance examples In 10](https://reader035.vdocuments.site/reader035/viewer/2022071104/5fddab23172a780a612b9f24/html5/thumbnails/1.jpg)
스핀토크 Summer School2008. 7. 2 - 4
수송특성 측정방법수송특성 측정방법
서 강 대 학 교서 강 대 학 교
극한양자물성연구팀
정 명 화
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Contents
• DC measurement : Electrical resistanceH ll ff t ( l l i: Hall effect (normal, anomalous, spin
Hall)& simultaneous MR curve
• AC measurement: dV/dI measurement
& simultaneous I-V curve• Sample preparation
• RF measurement: Van der Pauw method
• Sample preparation
vs. timevs. frequency
Sample preparation
• Applications: Waveguide structure
: Magnetic rf oscillator: Magnetic rf oscillator: Spin diode: Domain wall motion
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DC measurement
Current bias Voltage bias
V = I Rsmall
V = I Rlarge
control
measure
gcontrol
measure
I
V
Four-probetechnique
Two-probetechnique I
V
Itechnique
I
technique I
I
VV
I
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Hall effect
F = q v X B ; Lorentz forceF q v X B ; Lorentz force
For a bar-shaped semiconductor,H ll ffi i t
B
Hall coefficient
RH = |VH | d
I B
- - - - - - - - - - - -
+ + + + + + + + + +ICarrier density
I B
VH n = I B
q |VH | d
VH < 0 : n-type
V > 0 p type
Hall mobility
μ =|VH | d
VH > 0 : p-type μ ρ I B
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Hall measurement
Four-probe technique Five-probe technique
I+ I-
V-
I+ I-
V-
I+ I-
V-
I+ I-
Va+ Vb+
I+ I
V+ B B
I I
V+ B
V+(Va+) – (Vb+) = 0VTot = VH + VMR
offset
Hall bar-shaped filmHall bar-shaped film
Vb- Vc-Va- HallVH = (Va+) – (Vb–)
I+ I-
H ( ) ( )
MRVMR = (Va+) – (Vc+)
Vb+ Vc+Va+ B or (Va–) – (Va–)
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Hall and MR measurement
I+ V-
RRT
V+ I-
R MR + RMR
RT = MR + RH
RT(+) = MR + RH
R ( ) MR RRHRT(−) = MR − RH
RT(+) + RT(−)MR = H
H
MR 2
RT(+) − RT(−)RH =
H
RH 2
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Sample preparation
Cloverleaf
For an arbitrarily shaped sample,
CloverleafSquare or rectangle
Preferred Acceptable Not recommended
• Ohmic contact quality
• Sample uniformity
Important concerns
• Permanent magnet
C t
Equipment required
Sample uniformity
• Sample size ≫ contact size &
sample thickness• I < (200 R)-0.5
• Current source
ex. GaAs (ρ ~ 107 Ωcm) : 1nA
• High impedance voltmeter
• Measurement consistency • Temperature controller
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Van der Pauw technique
Resistivity measurement Hall measurement
R V / I
I V1 4 VRA = V43 / I12
2 3
I
I1 4
I
V
1 4
RB = V14 / I23
2 3
B2 3
B 14 23
exp(-π RA/RS) + exp(-π RB/RS) = 1 I13 (1 → 3) : V = VH = V24P
n = I B
q |VH |dρ = RS d |VH | d
μ = | H |ρ I B
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Example of typical dataExample of typical dataExample of typical data
1
2 3
4
Resistivity Hall voltage2 3
I21 V34 R21,34 .I12 V43 R12,43 .I43 V12 R43 12 .
+B fieldI13 V24P .I31 V42P .43 12 43,12
I34 V23 R34,23 .
I32 V41 R32,41 .I V R
31 42PI42 V13P .I24 V31P .
B fieldI23 V14 R23,14 .I14 V23 R14,23 .I41 V32 R41,32 .
−B fieldI13 V24N .I31 V42N .I42 V13N .42 13NI24 V31N .
exp( π R /R ) + exp( π R /R ) = 1
RB .RA .
n = 8 I B / q | ΣV |
RS = . nS = .
exp(-π RA/RS) + exp(-π RB/RS) = 1 nS = 8 I B / q | ΣVi |
μ = 1 / q nS RS = .ρ = RS d = . n = nS / d = .
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Anomalous Hall effect
VH = (R0H + R1M) I / t
extraordinary Hall
ordinary Hall
y(anomalous Hall)
30
DMS thin film
1
unit
)
10
20
cm3
) R1
R0
1
0
RH (
arb.
20
-10
0
M (
emu/
0
-2 -1 0 1 2
-1
H ( T )
-2 -1 0 1 2-30
-20
H ( T ) H ( T )( )
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Spin Hall effect
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AC measurement
V
& simultaneous I-V curve
Waveform synthesizer
VO
DC signal → I – V curve
Mixer/adder Standard resistor Sample
R R
Vacsinωt
Lock-in amplifierI
V
RSR RS
VSR VSVO + Vacsinωt
RSRIO + RSRIacsinωtVS(IO) + ·Iacsinωt
dVS
dIVS(IO) IacsinωtdI I = Io
AC signal → dV/dI curveAC signal → dV/dI curve
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RF measurement
DC source
DC
70x130 nm2
Bottom electrode
Ground
Bias teeDC
70x130 nm2
Top electrodeSignal
RF
RF + DC
MSUGround
RF
Oscilloscope Spectrum Analyzer
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RF measurement
DC source
DC Bottom electrode
Ground
Bias teeDC
100x200 nm2
Top electrodeSignal
RF
RF + DCAISTGround
RF
Oscilloscope Spectrum Analyzer
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RF measurement
DC source
DC Bottom electrode
Ground
Bias teeDC
W = 500 nm
Top electrodeSignal
RF
RF + DC
KISTGroundRF
Oscilloscope Spectrum Analyzer
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Remarks for RF measurement
• You have to measure background signal.g g
• You have to use rf preamplifier.
0.6
0.7
Experimental data
500
400
0.4
0.5
μV/H
z-1/2 ) Experimental data
B k d i l
400
300
age
()
킮
With preamp.
0 1
0.2
0.3
PS
D ( μ Background signal
E B k d
200
100V
olta
0 2 4 6 8 100.0
0.1
Frequency ( GHz )
Exp.- Background 100
2520151050
Frequency (GHz)
Without preamp.
Frequency ( GHz ) Frequency (GHz)
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Constant voltage mode
-I
RF pre-amp55dB
Bias-T55dB
up to 18 GHz
1kΩMagnetic SpectrumAnalyzer
1kΩMagnetic Field
Ru (0.85)+
D.C. bias voltage1.5 V battery
unit : nm e-
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Constant current mode
Bias-Te-
RF pre-amp55dB
e
55dBUp to 18 GHz
i
Constant
SpectrumAnalyzer
Magnetic Field
Ru (0.85) VoltmeterConstant
Current SourceI = 1 mA
unit : nm+I
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Field dependence of magnetic noise
A14
I = -1.25 mA
300 K
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Current dependence of magnetic noise
H = 60 Oe
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Temperature dependence of magnetic noise
8
300 K -100 Oe
2 )
H > Hc H < Hc
4
6
4.2 K, -100 Oe150 K, -100 Oe300 K, 100 Oe
( nV
/Hz1/
2
2
4
oise
PS
D
0 4 8 12 160N
o
Frequency ( GHz )
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RF measurement with sweeping current & measuring dV/dI
Lock-in ref.1 009 kHz1.009 kHz
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Magnetic rf oscillation
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Current and field dependence of magnetic rf oscillation
Current = 14 mA (T = 3 K) Magnetic field = 6.1 kOe (T = 3 K)
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Magnetic rf oscillator I
DC+RF RF
Bias tee
RF pre-amplifier
DC bias
DC
SpectrumAnalyzer
DC biasvoltage
H
Analyzer
Output(0.8~1.2 T)
F. B. Mancoff et al. Nature 437,393 (2005)
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Magnetic rf oscillator II
RF
RF pre-
Bias teeDC
RF preamplifier
SpectrumAnalyzer
IA
75o
Output
Analyzer
IBH
Bias teeDC(740 mT)
RF
S. Kaka et al. Nature 437,389 (2005)
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Spin diode
AIST
RFDC
AIST
(200 MHz~15 GHz)(200 MHz 15 GHz)
Output
A. A. Tulapurkar et al. Nature 438,339 (2005)
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Domain wall motion
50 Ω
RF pre-amplifier
OscilloscopeH
Bi t
Pulsegenerator Output
Bias tee
Idc With field
M. Hayashi et al. Phys. Rev. Lett. 96, 197207 (2006)
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Magnetic Property Measurement System
2008.12.
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System performance examples
In 10 min. cooling from 300 K to stable 10 KRMS i < 4 X 10 8In 2 min. cooling from 10 K to stable 1.8 K RMS noise < 4 X 10-8 emu
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Magnetic & transport measurement systems
+ Transport measurements (개발중)+ Transport measurements (개발중)for LR (~nV level) & HR (~100 fA level)materials
+ dV/dI (RS830)
2009. 1.
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Memory switching time measurement system
+
• 4 probes
• CCD camera
• 3-axis magnetic field
• Each magnet ~ 1 kOe
• Vibration-free table
• Shield box
• Water cooled system
• High power supply
2008. 9.
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Pulse pattern test
• Arbitrary waveform generator (120 MHz)
: Agilent 81150A
• Oscilloscope (1 GHz)
: Agilent 7104A: Agilent 7104A