스핀토크 Summer School 2008. 7. 2 - 4 수송특성 측정방법 수송특성 측정방법 서 강 대 학 교 서 강 대 학 교 극한양자물성연구팀 정 명 화
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스핀토크 Summer School2008. 7. 2 - 4
수송특성 측정방법수송특성 측정방법
서 강 대 학 교서 강 대 학 교
극한양자물성연구팀
정 명 화
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
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
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
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–)
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
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
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
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 = .
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 )( )
Spin Hall effect
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
RF measurement
DC source
DC
70x130 nm2
Bottom electrode
Ground
Bias teeDC
70x130 nm2
Top electrodeSignal
RF
RF + DC
MSUGround
RF
Oscilloscope Spectrum Analyzer
RF measurement
DC source
DC Bottom electrode
Ground
Bias teeDC
100x200 nm2
Top electrodeSignal
RF
RF + DCAISTGround
RF
Oscilloscope Spectrum Analyzer
RF measurement
DC source
DC Bottom electrode
Ground
Bias teeDC
W = 500 nm
Top electrodeSignal
RF
RF + DC
KISTGroundRF
Oscilloscope Spectrum Analyzer
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)
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-
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
Field dependence of magnetic noise
A14
I = -1.25 mA
300 K
Current dependence of magnetic noise
H = 60 Oe
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 )
RF measurement with sweeping current & measuring dV/dI
Lock-in ref.1 009 kHz1.009 kHz
Magnetic rf oscillation
Current and field dependence of magnetic rf oscillation
Current = 14 mA (T = 3 K) Magnetic field = 6.1 kOe (T = 3 K)
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)
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)
Spin diode
AIST
RFDC
AIST
(200 MHz~15 GHz)(200 MHz 15 GHz)
Output
A. A. Tulapurkar et al. Nature 438,339 (2005)
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)
Magnetic Property Measurement System
2008.12.
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
Magnetic & transport measurement systems
+ Transport measurements (개발중)+ Transport measurements (개발중)for LR (~nV level) & HR (~100 fA level)materials
+ dV/dI (RS830)
2009. 1.
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.
Pulse pattern test
• Arbitrary waveform generator (120 MHz)
: Agilent 81150A
• Oscilloscope (1 GHz)
: Agilent 7104A: Agilent 7104A
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