Post on 04-Oct-2021
Spin transport in a semiconductor channel
Introduction
Channel and Device Structure
Spin Hall effect in a Rashba system
Results and Discussion
Conclusion
The spin transport device is one of the excellent candidates for next
generation technology.
The spinβorbit interaction in semiconductor systems provides an
exceptionally rich area of research. The spin-based semiconductor concept
may permit the fabrication of fully integrated spin-FET structures, and the
quantum well and nanowire systems have excellent properties appropriate for
low power devices.
Room temperature spin transport in a GaN wire
We show a direct demonstration of the spin Hall effect and demonstrate a
technique for an all-electric measurement of the DattaβDas conductance
oscillation using a quantum well system.
Complementary spin logic device
V
ππππ¦
V
Semiconductor spintronics
Quantum well channel
VH,1 VH,2 VH,3 VH,4
IVH,n
β¦..β¦VH,5
x = 0
β¦..β¦
BR
Semiconductor spin device
Low power solution
Low-dimensional channel
FM
WFM
WH
L
WC
A Aβ
A Aβ
80 nm 56 nm
110 nm
80 nm
3 nm
Buffer & lower
insulating barriers
Single quantum well
InAs heterostructure
Gate dielectric
Gate metal
Ferromagnet
Gate coverage
Gate coverage
1 ΞΌm
Semi-insulating InP(001) sub
In0.52Al0.48As 300nm
n+ In0.52Al0.48As 7 nm (n = 4Γ1018)
In0.52Al0.48As 6 nm
In0.53Ga0.47As 13.5 nm
In0.52Al0.48As 20 nm
InAs 2 nm
In0.53Ga0.47As 2.5 nm
InAs (Quantum Well) 2 nm
I
x
VH
0
x = 0
0.6 0.8 1.0 1.2 1.4 1.6 1.8
-40
-20
0
20
40
experimental data
fitted line
ideal ballistic
V
H / I (
m
)
L (m)
Parallel-type spin transistor (P-ST)
βHighβSource Drain
ONOFF
When precession = 180
β ON (p-MOS like)
Antiparallel-type spin transistor (AP-ST)
βLowβ βHighβ
ON OFF
When precession = 360
β ON (n-MOS like)
0
10
-3.0 -2.5 -2.0
0
5 VAP
V
β V
0 (
V)
VP
VIN
(VG) (V)
-3.0 -2.5 -2.0
0
10
20
VIN
(VG) (V)
VO
UT (
V)
0 2 4 6 8 10 12
-30
-20
-10
0
10
20
30
VIN
(VG)
1 V
VOUT
VAP
VP
VO
UT (
V)
Time (sec)
I
VP+
β
+
VAP +
β
β
VG
P-STAP-ST
L
2 ΞΌm
VOUT
AB-type AA-type
-1.0 -0.5 0.0 0.5 1.0-50
0
50
100
150
200
250
300
350
V (
V)
H (kOe)
300 K
200 K
150 K
100 K
77 K
50 K
30 K
10 K
I = 1 ΞΌ A
I
1D and 2D spin devices are fabricated
for room temperature applications.
We demonstrate complementary spin transistors consisting of two types of
devices, namely parallel and antiparallel spin transistors using InAs based
quantum well channels and exchange-biased ferromagnetic electrodes.
We realize a complementary logic operation purely with spin transistors
controlled by the gate voltage, without any additional n- or p-channel
transistor.
We present spin injection in single-crystal gallium nitride nanowires and
report robust spin accumulation at room temperature.
Spin injection efficiency depends on crystal direction of GaN wire.
Spin Hall device is fabricated using
Rashba system for low power applications.
W. Y. Choi et al., Nat. Nanotech. 10, 666 (2015)
T.-E. Park et al., Nat. Comm. 8, 15722 (2017)
Y. H. Park et al., Sci. Rep. 7, 46671 (2017)
Thin body p-GaAs junctionless FET
on Si via wafer bonding
and epitaxial lift-off technology
Integration of III-V compound semiconductors on Si
Electron mobility
Hole mobility
β’ Enhanced carrier mobility, switching speed, higher on-current and faster operation
β’ n-type JL FET is previously reported, however, p-type JL FET is rarely reported.
Introduction
Effective mobility calculation considering contact and channel resistance
Experimental Results
Fabrication process of thin body p-GaAs junctionless FET on Si
Transfer (ID-VG) curve of p-GaAs OI on Si FET varying the channel thickness
Effective mobility extraction from ID-VG curve varying channel length
p-GaAs OI on Si FET from 10 to 40 nm of channel thickness
S.S. enhancement with Y2O3 surface passivation
Transfer (ID-VG) and Output (ID-VD) curve of p-GaAs OI on Si FET
Transfer and output curve of channel thickness 20 and 30 nm
Effect of top surface passivation by Y2O3
β’ High Ion/Ioff ratio is obtained for 20 and 30 nm of channel thickness
β’ Trade off between Ion and S.S.
Conclusion
p-GaAs OI on Si using patterned-wafer bonding and epitaxial lift off
β’ As the channel thickness increases, on-current increases.
β’ Subthreshold swing (S.S.) is reduced as the channel thickness is increased.
β’ Ion/Ioff is defined by ~10 in the case of ~40 nm of channel thickness.
β’ 10 nm of channel showed presented lowest Ion current level (~nA scale).
β’ Patterned wafer bonding for fast ELO and back-gate device fabrication.
β’ Channel thickness optimization (10 to 40 nm, 10 nm interval).
β’ Varying channel length from 2 to 50 um (to accurately calculate effective mobility).
β’ High Ion/Ioff ratio : ~105
β’ The ratio of contact and channel resistance is plotted varying gate bias.
β’ Effective mobility is calculated excluding S/D contact resistance.
β’ The highest Ion/Ioff ratio : ~106 β’ Enhanced S.S. : ~250 mV/dec
β’ We firstly reported thin body p-GaAs OI on Si FET using wafer bonding and ELO.
β’ Channel thickness is a critical factor to define device performance.
β’ In 30 nm thickness, Ion/Ioff and S.S. are measured by ~105 and 420 mV/dec, respectively.
β’ Surface passivation further enhanced Ion/Ioff (~106) and S.S. (250 mV/dec) .
Junctionless (JL) FET β’ Low cost and mass production
(simple fabrication steps)
β’ Minimizing mobility degradation
(caused by surface scattering and phonon
scattering)
β’ Low Off-current by using full depletion
β’ No doping gradient -> use for small
dimensionJ-P Colinge et.al., Nature nanotechnology (2010)
Thin n- and p- GaAs channel CMOS on Si
Biomimetic Electronic Materials
for Human-Interfacing Sensors and Devices
Introduction
Biomimetic Electronic Materials
Conclusion
We have shown that employing biomaterial-incorporated conductive nanonetworks as interfacial
layers of contact based resistive pressure sensors produced giant piezoresistive response via effective
modulation of interlayer resistance and enabled simultaneous ultrasensitivity and broad operating
pressure ranges.
Nanomesh-based wearable bio-sensing platformWearable Devices
Biological glue and hydrodynamic assembly of nanomesh
* μ°¨μΈλμ¨μ΄λ¬λΈμνν©κ³Όλ―Έλκ·Έλ¦¬κ³ μ΄μ, μ£Όκ°κΈ°μ λν₯ (2014) * Vandrico. Inc. Wearable Tech Market Insights (2014)
Wearable devicesHealthcare
Entertainment
Houseware
Rehabilitation
Augmented realityMilitary purpose
Smart phones
< Applications and statistics of wearable devices >
Nat. Nanotechnology, 6 13 (2011)
www.viatechnology.com, www. gizmodo.com, www.graco.com.
ElectricalIonic
Chemical
Biological
Mechanical
Human-Interfacing Sensors for Healthcare
β’ Highly conductive (electronic, ionic)
β’ Enabling additional biological functionalization
β’ Well adherent on flexible substrates or metallic layers
β’ Flexible and mechanically stable
β’ Biocompatible
β’ Water-stable
Nanostructured Hybrid Materials System
: Biomimetic Electronic Materials
< Materials Requirements >
Biomimetic Approach
< Biomolecular recognition >
http://en.wikipedia.org/wiki/Molecular_recognition
Single-stranded DNA (ssDNA) of M13 virus.
Molecular recognition refers to
the specific interaction between
two or more molecules through
non-covalent bonding such as
hydrogen bonding, metal
coordination, hydrophobic forces,
van der Waals forces, pi-pi
interaction, halogen bonding, etc.
< Biological template: M13 phage >
Scientific Reports, 5 9196 (2015)
< Bio-panning process > < Nanomesh of SWNTs using biological glue >
Adv. Mater. 27 922 (2015)
Wearable Physiological Electrodes
We found a surface peptide sequence of a
filamentous biopolymer that showed strong
binding affinity toward SWNTs. The
biopolymer serves as biological glue
< Contact impedance measurement >
Adv. Mater. 27 922 (2015)
< High frequency brain signal measurement >
Adv. Mater. 27 922 (2015)
Nanomesh-integrated flexible neural probes
Flexible/Wearable Chemical Sensors
< Hydrodynamic assembly + LBL assembly >
a
b c
Adv. Mater. 28 1577 (2016)
< Smart contact-lens>
< Nanomesh-based enzyme platform for high-performance wearable biosensors >
Flexible/Wearable Pressure Sensors
Flexible pressure sensors based on biomimetic interfacial layers
ACS Appl. Mater. Inter. (2017)
Monitoring of wrist pulse wave
Conductive nanomesh with a high effective-surface-area and strong adhesion to substrates could
enable the study of biologically important but weak brain signals using a non-invasive platform.
Adv. Mater. 28 1577 (2016)
We have developed a biological template material-based biosensing platform with unprecedented
applicability and versatility. The nondestructive assembly of nanostructured enzyme platform in
combination of specific biomolecular attraction and electrostatic coupling using a biological
template material enabled flexible biosensors.
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4
-50
-40
-30
-20
-10
0
10
20
30
0 250 500 750 1000-38
-36
-34
-32
0mM Glu
0.25mM Glu
0.5mM Glu
0.75mM Glu
1mM Glu
Cu
rre
nt
(A
)
Voltage (V vs. Pt pseudo RE)
Cu
rren
t (
A)
Glucose concentration (M)
Sensitivity
~113 Β΅A/mM cm2
GlucoseConcentrationincrease
A genetically engineered biological template-based approach for the
assembly of a nano-structured hybrid electronic material system,
biomimetic electronic materials, has been successfully developed and its
applications to wearable/flexible sensors and devices have been
demonstrated.
Biomimetic electronic materials have huge potentials for the development
of wearable health-monitoring devices, personalized medicines, human-
machine interfaces, prosthetic limbs, and intelligent robotics.
*Done in collaboration with Dr. J. H. Choi (KIST)
A fundamental diffusion-based
hydrodynamic phenomenon in combination
of biological glue can successfully assemble
a large-scale conductive nanomesh.
2
Project Description
Device Preparation
2
Spin Torque Ferromagnetic Resonance
The ST-FMR can measure ππ·πΏ, ππΉπΏ and πΌ simultaneously.
The IRF in Pt generates the filed-like and anti-damping torques as well as the
Oersted field.
Spin orbit torques (SOTs) : Field-like torque (ππΉπΏ) β mΓ yAnti-damping torque (ππ·πΏ) β mΓ y Γm
ππππ₯ π» = πππ₯π»2
π» β π»πππ 2 + π₯π» 2
+ ππ΄π» β π»πππ π₯π»
π» β π»πππ 2 + π₯π»2
Symmetric Lorentzian : ππ·πΏ Asymmetric Lorentzian : ππΉπΏ + πππ(π»πππ : resonance field, π₯π» : half width half maximum)
FM (t)
MgO(2)Ta(2)
Ta(0 or 1)Pt (5)
SiOx
300 700 1100 1500
-8
-4
0
4
Data
Fit
Asym
Sym
vm
ix (
V)
Hext
(Oe)
2
Spin-Transfer Torque and
Spin-Orbit Torque
Spin-Hall Angle / Magnetic Damping
2
0 5 10 15
0.00
0.05
0.10
0.15
Pt|Co
Pt|CFB
Pt|Py
D
L
vo
lta
ge
tFM
(nm)
Estimation of ππ·πΏ and ππΉπΏ from several ST-FMR analysis methods
Investigation of Ξ±, ππ·πΏ and ππΉπΏ for various Material / Interface / Thickness
Study of angular and temperature dependence
0 5 10 15
0.0
0.1
0.2
Pt|Co
Pt|CFB
Pt|Py
F
L+
Oe
vo
lta
ge
tFM
(nm)
Intercept, ππΉπΏ
Slope, πππ
To understand physics of spin-transfer torque & spin-orbit torque phenomena
To advance STT- and SOT-MRAM technologies
Spin-torque ferromagnetic resonance (ST-FMR)
Current-driven in-pane and perpendicular magnetization switching
Spin-torque nano-oscillators and wireless communication
Second Harmonic Hall measurement
Propagating Spin-Wave spectroscopy
βπ» = βπ»0 +2ππΌπππ
πΎπ (Ξπ»0 : inhomogeneous line width broadening)
Perpendicular magnetization Switching
0 5 10 150
50
100
150 PtCFB2
PtCFB3
PtCFB4
PtCFB5
PtCFB7
PtCFB10
H
(O
e)
f (GHz)
0 5 10 150.00
0.02
0.04
0.06
Pt/Co
Pt/CFB
Pt/Py
eff
tFM
eff (nm)
-400 -200 0 200 400-0.30
-0.15
0.00
0.15
0.30
Hz (Oe)
r H (
)
Hx
Idc
Free MagnetTunnel Barrier
Fixed Magnet
SOC Metal
READ
WRITE
-2000 -1000 0 1000 2000-4
-2
0
2
4
I sw (
mA
)
Hx (Oe)
ΞΈ
x
y
HD
Hk ΞΈ
Hx
HR
In-plane Current-driven switching
Various phenomena are involved during the perpendicular magnetic switching driven by in-plane
currents; DL-SOT, FL-SOT, Hext, DMI, Domain Nucleation/Propagation, PMA and so on
Spin torque nano-oscillators
2
In-plane magnetic switching in 3-terminal MTJ
Junction size80 nm x 200 nm
-15 -10 -5 0 5 10 1535
40
45
50
R (
k
)Field (mT)
-3 -2 -1 0 1 2 335
40
45
50
0mT
R (
k)
Current (mA)
Field-Driven switching
Field-Driven switching Current-induced switching
Switching phase diagram
β’ RA = 1~5 Ξ©β2
β’ Annealing @ 300 oC, 30 min 4 kOe, easy-axis direction
β’ Ion-milling stopped in the middle of the CoFeB(5 nm)
β’ Dumbbell shape pillar fabrication
Stray field
MgO
CoFeB(2)
Ru(0.8)
100 150 200 250 300 350 400
4
6
8
10
12
Magnetic field (Oe)
Fre
qu
en
cy (
GH
z)
0.000
1.250
2.500
3.750
5.000
6.250
7.500
8.750
10.00
Field Sweep (420 to 80 Oe, 85o),I = 2.0 mA Current Sweep (1.4 to 3.3 mA), H = 400 Oe,
85o
Sputtering/Evaporation E-beam/Photo-lithography/Ion-milling
Electric field induced magnetic anisotropy
modulation at CoFeB-MgO interfaces
Introduction
Experiments
Magnetic properties of Ta/CoFeB/MgO and Hf/CoFeB/MgO
Results and Discussion
Conclusion
Electric-field-induced modification of magnetic anisotropy is studied
using voltage dependent TMR and XRMS measurements.
The electric field induced magnetic anisotropy change is significantly
enhanced by inserting ultrathin heavy metals suggesting that interface
engineering could be used to enhance the electric field-induced magnetic
anisotropy modulation of ultrathin ferromagnetic films
Electric field control of magntism has been studied extensively recently due
to its potential use for low-power magnetization swtiching in spintronics
devices. In MgO-based magnetic tunnel jucntions(MTJs), electric field has
been used induce magnetization switching even in the absense of electric
current induced spin transfer torques.
The underlying physics behind this phenomena is still controversial and needs
to be clarified.
Insertion and buffer layer dependence of the electric field effect
The positive slope in magnetic anisotropy vs. voltage plot implies that the PMA is
strengthened when the electron density is increased, while it is weakened when the
electron density is decreased.
The change of magnetic anisotropy energy per electric field is significantly enhanced
by inserting heavy metals (e.g. Hf, Ir, Ru). Also, the electric field effect is opposite for
Hf-buffered (left) and Ta-buffered (right) MTJs.
Electric field dependence of TMR
The TMR of the CoFeB/MgO/CoFeB shows a strong voltage dependence.
HK of the bottom CoFeB (weakly in-plane) is decreased with increasing applied voltage,
indicating that the interfacial PMA of the bottom CoFeB increases with voltage.
A similar effect appears when a ultrathin (0.5ML) Hf layer is inserted between the bottom
coFeB and MgO.
Switching magnetism with electric field
Electric field induced magnetic anisotropy modulation
The electric field induced change in magnetic anisotropy was determined by measuirng
the voltage dependent TMR in MTJ devices
Depth-resolved, element-resolved, and magnetic sensitive XRMS was used to varify
the mechanism of the electric field control of the magnetic anisotropy.
TMR of a CoFeB/MgO/CoFeB MTJ device
Ta(Hf)/CoFeB/MgO thin films show strong strong perpendicular magnetic anisotropy
(PMA) for CoFeB thickness tCoFeB < 1.1nm indicating strong PMA at the CoFeB-MgO
interface.
TMR of 10 micron sized CoFeB (1.2nm)
/MgO(1.6nm)/CoFeB(1.3nm) MTJ device.
The top CoFeB has strong PMA while the
bottom CoFeB shows weak in-plane
mangetic anisotropy.
The magnetic anisotropy can be
determined from the saturation field (HK).
XRMS measurement of electric field induced anisotropy modulation
XRMS measurements reveals that the remanent magnetization changes with voltage.
Further measurements and analyses are required to fully understand the interface
sensitive nature of the electric field effect utilizing interface sensitive and depth resolved
XRMS.
RE
FM
Ferrimagnetic Skyrmion
Magnetic Skyrmions for Next
Generation Electronics
Introduction
Experiments
Conclusion
Topological protection and atomic size
Statics/Dynamics of room temperature ferromagnetic skyrmions
In ferromagnetic heterostructures, magnetic skyrmions can be stabilized at
room temperature and also be displaced at a speed exceding > 100 m s-1
Dynamic excitation behaviours of magnetic skyrmions can be excited and
controlled upon the application of nanosecond spin-orbit torques
Magnetic skyrmions exhibit fascinating properties
Soft X-ray Transmission Microscopy β MTXM & STXM
Both MTXM and STXM utilizes XMCD effect, and they offer 25 nm spatial and
70 ps temporal resolutions. These facilities are only available at synchrotrons
In principle, circularly-polarized X-ray interacts differently with up-magnetized
and down-magnetized electrons due to their different angular. Therefore, in the
presence of magnetic textures, the transmitted X-ray contrasts differs for
opposite magnetizations
S. Heinze et al., Nat. Phys. 7, 713-718 (2011)
X.Z. Yu et al. Nature 465, 901-904 (2010) T. Schulz et al., Nat. Phys. 8, 301-304 (2012)
N. Nagaosa et al., Nat. Nanotech. 8, 899-911 (2013)
A. Soumyanarayanan et al., Nat. Mater. 16, 898-904 (2017)
X. Zhang et al., Sci. Rep. 5, 9400 (2015)
Y.Q. Huang et al., Nanotechnology, 28 (2017)
: Magnetic skyrmions are topologically-
protected, and can be defined by the
topological number S (or skyrmion
number). When they appear, their size
can be as small as a single nanometer
Ultralow threshold current density
: Threshold current density for the
driving magnetic skyrmions is known
to be as small as ~106 A m-2, which is
104 times lower than that for domain
wall displacement
Emergent electrodynamics
: When electrons pass through a
magnetic skyrmions, they experience
emergent electromagnetic field due to
the topological nature of the skyrmion.
Such emergent field causes a distinct
phenomena, such as skyrmion Hall
effect
Device opportunities
: Owing to attractive characteristics of
magnetic skyrmions, low-power &
ultrafast skyrmionic device applications
could be realized β including skyrmion
memory, skyrmions logic and skyrmion
neuromorphic computing devices
Results and Discussion
Magnetic skyrmions can be
deterministically written and
deleted by the application of
asymmetric bipolar pulses along
a nanowire track
Topological changes accompany
the generation and deletion of
topological defect, vertical
Bloch line (VBL), which plays
crucial role during the processes
S. Woo et al., Nat. Mater. 15, 501-506 (2016)
Materials;
[Pt3/Co0.9/Ta4] 15
[Pt3/CoFeB0.9/MgO1.8] 15
Deterministic writing/deleting of skyrmions
Ferrimagnetic skyrmions without skyrmion Hall effect
Schematic description Scanning Transmission X-ray Microscopy (STXM) and the principle of X-ray magnetic circular dichroism (XMCD)
Synchrotrons
BESSY II in Berlin, Germany
Beamline: MAXUMUS (STXM)
ALS in Berkeley, USA
Beamline: XM-1 (MTXM)
SLS in Villigen, Switzerland
Beamline: PolLux (STXM)
j > 0
j < 0
Materials;
[Pt3/CoFeB0.9/MgO1.8] 20
Skyrmion Breathing
Skyrmion Translation
Pulse Profile
S. Woo, K. M. Song et al., Nat. Commun. 8, 15573 (2017)
1 2 3
0
20
40
S
kH
E ()
ja (1011 A m-2)
Exp.
Sim. (w/o defects)
Sim. (w/ defects)
1 2 30
20
40
60
Velo
city (
m s
-1)
ja (1011 A m-2)
Exp.
Sim. (w/o defects)
Sim. (w/ defects)
In ferrimagnetic materials, such
as GdFeCo,
antiferromagnetically-coupled
ferrimagnetic skyrmions can be
stabilized and driven without
experiencing skyrmion Hall
effect, resulting in the straight
motion along a nanowire track
Materials; [Pt3/GdFeCo5/MgO1] 20
S. Woo, K. M. Song et al., under review
(priprint available at arXiv: 1703,:10310)
Spin waves for the efficient displacement of magnetic skyrmions
Magnetic domain wall can be efficiently
driven by the burst of spin waves, which
are generated by the collision of two
adjacent domain walls
The results imply that spin waves could be
an efficient source for skyrmions motion
Materials; Ni80Fe20 (Permalloy)
Schematic of spinwave-driven motion of ma
gnetic skyrmions
[Nanotechlogy 26, 225701 (2015)]
Spinwave-driven displacement of domain walls
S. Woo et al., Nat. Phys. 13, 448-454 (2017)
Our investigations reveal that magnetic skyrmions could really be
incorporated into useful devices in the near future
S. Woo, K. M. Song et al., under review
(priprint available at arXiv: 1706,:06726)
935 940 945 950 955 960
-1.0
-0.5
0.0
0.5
1.0
V/V
a (norm
.)
Time (ns)
Deleting pulse
-5 0 5 10 15 20
-1.0
-0.5
0.0
0.5
1.0
V/V
a (norm
.)
Time (ns)
Writing pulse
Time
Q=0
Q=1
Time
Q=1
Q=0
Sk1
Sk4
Sk2
Sk3
Sk1
Sk4
Sk3Sk2
Sk7
Sk1
Sk4
Sk3Sk2
Sk5
Sk6 Sk7
Sk5
Sk6
Sk2
Sk7
Sk2
Sk7
Sk2
Sk2 Sk2 Sk2 Sk2
Au
Sk5
Sk6
Sk2
Sk7
Sk5
Sk7
Materials; [Pt3/GdFeCo5/MgO1] 20