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Electronic Properties ofElectronic Properties of Metal-Insulator Interfaces
Hermann Kohlstedt
Forschungszentrum JülichInstitut für Festkörperforschung
GermanyGermany
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Famous Comments about Surfaces and Interfaces
Wolfgang Pauli"God made solids but surfaces (and interfaces) were the work of the Devil "God made solids, but surfaces (and interfaces) were the work of the Devil.
This (very popular) quotation exists in a great variety of versions.
...in such a way the transition region or interface between the Herbert Kroemer
Nobel Lecture: Quasielectric fields and band offsets:
different materials plays an essential role in any device action. Often, it may be said that the interface is the device.
Nobel Lecture: Quasielectric fields and band offsets: teaching electrons new tricks, Rev. Mod. Phys. 73 (2001).
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The MOSFET as an ExampleThe MOSFET as an Example
Others:Others:Laser Diode, Giant Magneto Resistance (GMR) DeviceMagnetic Tunnel Junctions, pn-Diode, Josephson junctions...
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1 The MOSFET
Metal Oxide Semiconductor Field Effect Transistor
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A Historical Remark
19261926MOSFET Patent: J. E. Lilienfeld, US Patent 1.745.173 (1930)
19461946Bipolar transistor?
1960First working MOSFETD Kahng and M M Atalla Pittsburgh 1960
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D. Kahng and M.M. Atalla, Pittsburgh 1960
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Computer: An Interface Story1959 first planar transistor
1961 first integrated circuit (IC)
1964 IC5 transistors
1968 IC array 180 Transistors
1978 CPU20000 transistors
1985 CPU 200000 transistors
2000 CPU - Pentium III 28.000.000 transistors
2008820 Millionen Transistors
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The Metal Oxide Semiconductor Capacitor
MOS-Capacitor
Work functionGate metalSiO2
Work functionEnergy gapBand structure
Silicon (Si) Interface statesDefectsDevice fabricationDevice fabrication...
Why it took more than 30 years to realize a MOSFET?
...the MOS cap was a „hard nut“ - in preparation and in understanding!!
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...the MOS cap was a „hard nut in preparation and in understanding!!
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High Resolution TEM of Gate StackTEM: Transmission Electron Microscopy
Gate
SiO2
Channel
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D. A. Buchanan, IBM J. Res. Develop. 43, 245 (1999)
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Surface and Bulk Atoms
„Atom“1 nm
0.3 nm
1
1 nm0.3 nm
0.3 nm
1 nm
1 nm 1µm 1 mm
nVvolume atoms: 1 2 x 1010 2 x 1019
ns surface atoms: 26 5 x 107 5 x 1013
RelationnV/(nV+nS): 0.96 2 x 10-3 3 x 10-6
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Corner Atoms: 8 8 8
Down scaling increase importancs of surface!!
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Outline
Vacuum
Bulk Metal
Vacuum StepAdsorbate
Metal
Metal 2 Semiconductor Metal Ferromagnet
Metal 1
Metal 2
Metal
/Insulator
Metal
Ferroelectric
Ferromagnet
Ferroelectric
Metal Ferromagnet
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Bulk MetalMetal
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Energy Bands in Solids
Free electrons
ESchrödinger equation:
Ene
rgy
d2 ψ+
2 mψ [ E V( )] 0
V = V(x); only space dependence
ctro
n E
dx2 + h2
ψ [ E – V(x)] = 0
Ele
cSolution for V = 0: free electron
2 Wavevector k E = h2 k2
2 m
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Confined Electron
En = h2 π 2
2 m L2n2
8 8
E Ψn=4
2 m LEigenenergies
rgy
E
E4
E
Ψ4
ergy
E
n=3
ectro
n en
e E3
E2
Ψ3
Ψ2ectro
n en
e
n=2
0 L
Ele
E1 Ψ1
2
Ele
n=1
0 L 0 L
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Finite Barrier Height
Ψ, VV = V00
Outside the box due to
xquantum mechanical tunneling
n = 1
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Kronig-Penny Model (1930)
A simple model to study the electron wave propagation in a crystal (1D)
V(x)V0
V(x) V(x) = V0 -b < x < 0
V(x) = 0 0 < x < a
x-b 0 a Atom
positions
Solution by solving the Schrödinger equation:
( )sin α a m: electron mass
positions
cos k a = cos α a + γ a ( )sin α aα a
γ =m V0 b α =
(2 m E)1/2
m: electron mass
h : Planck constant
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γ = h2
α = h E: energy of the electron
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Solutions of the Kronig-Penny Model
XX = cos α a + γ a ( )sin α a
α a2
1 allowed values
π 2 π 3 π 4 π
α a-1
of cos k a
-2γ a = π
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Kronig-Penny Model: Formation of Energy Bands
Energybandsn
Ene
rgy E
bands
Ele
ctro
n
2π/a-2π/a π/a-π/ak
2π/a-2π/a π/a-π/a
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Reduced Zone Representation
E
Ener
gy E
Elec
tron
Eg
k 2π/a-2π/a π/a-π/a π/a-π/a
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Energy Band Structure of crystalline Solids
Evac
φ
EF
Eg
EF
Metal Semiconductor Insulator
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Surface Science, K. W. Kolasinski. Wiley, 2004Fig. 1.9, p. 13
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Energy Levels in Si vs. Interatomic Spacing
Fig 3 16 Petty p 84Fig. 3.16 Petty, p. 84
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Metal-Vacuum Surface
Vacuum StepAdsorbate
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Definitions:
Surface: „Region“ between a material and vacuum
Vacuum
Material
Interface: „Contact region“ between a material A and a material B
Material A
Material B
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Vacuum
MetalMetal
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Characteristic Length Scales
Example:Metal Surface
++++++++++ ++++- - -
Vacuum_
+Surface dipole layer ++++++++++ ++++
+++++++++++++ Metal
+dipole layer
Spill-out effect of electrons at the surfaceSpill out effect of electrons at the surface
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The Jellium-Model
+++++-Metal Vaccuum
++++++ +-
- Spill-out effect of electrons at the surface
++++
Epot
Φpot
Work function : Energy to move an electronfrom bulk to vacuum (far away from the surface)
ΦEF
+ρ(x)
from bulk to vacuum (far away from the surface)
+ρ( )
Charge distribution
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- Henzler/Göpel p. 217
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Work function : Energy to move an electronΦWork function : Energy to move an electronfrom bulk to vacuum (far away from the surface)
Φ
EpotEvac
ΦEFEF
e-
Metal
x
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Three characteristic Length Scales
+ρ(x)
1: Atomic: Dipol layer
2: Micron: Image PotentialF =e2
(2x)2
-
V(x) = -e2
( )
(0.1nm)
(1 µm)
V(x)
V(x) = - 1/x 3 x 6 10-4 µm eV
4x
(1 µm) ( ) µ
3: Macroscopic(several µm)
3: Macroscopic
Φ1
Φ2
Work function:
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Work function:Move an electron several µm away from the surface
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Electron density vs. Distance (Fermi wavelength)
Friedel Surface
sity
Friedeloscillations
Surface
ron
dens
B lk
Ele
ct Exponential decay into vacuum
Bulk
Distance (in the order of the Fermi wave length, i.e. A)
Lang and Kohn: Phys. Rev. B 1, 4555 (1970).
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Surface Science, K. W. KolasinskiWiley, 2004, Fig. 1.10, p. 15
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Electron density vs. Distance (Fermi wavelength)
Lang and Kohn: Phys Rev B 1 4555 (1970) H Hövel University of Dortmund GermanyLang and Kohn: Phys. Rev. B 1, 4555 (1970). H. Hövel, University of Dortmund, GermanyFriedel-Oscillations observed near a step (Grahit at 5 Kelvin)
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Work Functions for various Metals
Dots: Experimental data
Dashed line: Theory, Jellium Model
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Lang and Kohn: Phys. Rev. B 1, 4555 (1970).
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Vacuum
Adsorbate(111)(110)
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Work Function and Crystal Orientation
f f t d bi
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fcc: face centered cubic
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Adsorbate Layer on a clean Metal Surface
Adsorbate layer
Vacuum
- - - --++++++++++++++++++++++++++++++++++++++++++++
Metal
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Adatom on a Surface
Evac
E3EF
φadsorbatΛ(E)
φclean
Γ
Evac
E2
Metal
( )
Metal
E1E s
Due to adatom on a surface:
x
-Shift of atomic levels-Broadening (Γ)-Shift of work function
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Henzler/Göpel, p. 474
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Work Function of Tungston vs. Crystal Orientation d Ab ti f Nitand Absorption of Nitrogen
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D. L. Adams and L. H. Gremer, Surf. Sci. 27, 21 (1971).
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Step
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Electrostatic Potential at a Step
The smoothed electronic surface leads to a reduced dipol moment near the step (perpendicular to the surface).Th f th k f ti i l ll d d th t
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M. D. Thompson and H. B. Huntington, Surf. Sci 116, 522 (1982).
Therefore the work function is locally reduced near the step.
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Work function vs. Step Densityφ
(eV
)Δφ
Step density (106 / cm)
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Step density (10 / cm)
K. Besocke, B. Krahl-Urban and H. Wagner, Surf. Sci. 68, 39 (1977).
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Dispersion Relation for free and Bulk Electrons
Perodic potential (bulk)Perodic potential (bulk)
Free electron
n E
nerg
y EE
lect
ron
2π/a-2π/a π/a-π/ak
2π/a-2π/a π/a-π/a
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Energy Levels: from Atoms to Solids
E
Atom Molecule Bulk (metal) crystal bulk and surface
Epot
EEss
EF
Eel
EF
kkπ/a π/a
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Surface States of a 3 D Crystal
Hypothetical electronic band structure of a crystal
E(k II) projected bulk band along k
Broken lines in the E(k II) plane indicate surface state bands in the gaps of the projected g p p jbulk-band structure, and surface resonances(degenerated with bulk states) –short doted lines
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From: H. Lüth, Surfaces and Interfaces of Solids, Springer, p. 79
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Bulk and Surface
EF
Ess
kπ/a
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Semiconductor
Metal 1
Metal 2
Metal
Semiconductor/Insulator
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Metal 2
Metal 1
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Metal-Metal Interface
E M t l 1 M t l 2EVac
E
EF
eΦ1 eΦ2
Metal 1 Metal 2
EF
EVc = Φ2 - Φ1
Vc : Contact potential (Volta voltage)
EF
c p ( g )
Galvani voltage
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Interface dipole layer
H. Lüth, Springer: Surfaces and Interfaces of Solids, 2001, p. 372
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Dimension of the Interface Dipole Layer
EVc Screening of charge imbalanace:
Positive ion cores and free electroncs
EF
Positive ion cores and free electroncs
Coulomb potential of a point charge:
Metal 1 Metal 2
p p g
Φ(r) = C/r exp (-r/rTF) with rTF ≈ 0.5 (n/a0
3)-1/6rTF 0.5 (n/a0 )rTF ≈ 0.5 A for Cu: n = 8.5 x 1022 cm-3
a0: Bohr radiusInterface dipole layer
ESimpified representation
EF
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H. Lüth, Springer: Surfaces and Interfaces of Solids, 2001, p. 373
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Contact Voltage: Examples
Ag: 4.33 eVg
Cu: 4.49 eV Clean well defined UHV experiment
Au: 4.83 eV
Vc = Φ2 - Φ1 Au – Ag (0.50 eV)
Not correct: over simplified model
Work function changes due to: atomic structure changes after contact relaxation/reconstructionWork function changes due to: atomic structure changes after contact, relaxation/reconstructionDifferent situation before and after contact
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Metal
Semiconductor
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The Schottky Contact
EVeΦS χ*SC
n-typ SemiconductorMetal(high work function)
EFEF
EVac
eΦM
CEC
EF
EV
EVac
EC
n-type depletion ρ = -ε0ε d2V/dx2
Poisson EquationEF
EFC
EV
Poisson Equation
Tutorial September 2008 Barcelona_H. Kohlstedt49
H. Lüth, Springer: Surfaces and Interfaces of Solids, 2001, p. 375
e-
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The Schottky Barrier
EV
n-typ SemiconductorMetalEVac
χSC Schotty Barrier:Ideal case:E χ*SC
eΦBeΦM
Ideal case:eΦB = eΦM - χSC
eVB
EFEFS = -dΦB /d χ SCS = 1 (slope parameter)
Nonmatching bondsSpace charge layerx
n-type depletion region (≈10 nm -100 nm)Screening length in a semiconductor(l l t th i t l)
Nonmatching bonds, surface states, impurities etc.are not considered
Space charge layer
Tutorial September 2008 Barcelona_H. Kohlstedt50
(less electrons than in a metal)
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Schottky and Bardeen Model
High density of interface states
Schottky model (ideal case), too simpleW. Schottky, Z. Physik 113, 123 (1938).
What means Bardeen approach?Phys. Rev. 71, 717, (1947)
no interface states
Tutorial September 2008 Barcelona_H. Kohlstedt51
H. Lüth, Springer: Surfaces and Interfaces of Solids, 2001, p. 376
Barrier heights of Si-Schottky contacts vs. work functions
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Bardeen approach to explain the Barrier Height
EVac
n-typ SemiconductorMetal
Δ
χSCE
Δ Interface dipole energy
S = -dΦB /d χ SCS 0 ( l t )
EFEF
S = 0 (slope parameter)due to pinning of EFΦB
EFF
Interface states: EF pinning
Space charge layer10 nm – 100nm
5 A X (not to scale)
Tutorial September 2008 Barcelona_H. Kohlstedt52
Surface states of clean semiconductor persists under metal overlayer (EF pinning)
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Qualitative Explanation of Surface (Interface) States
ConductionAtom
A
Conduction band
Due to different bonding
Acceptor
Surface state
B
conditions to bulk atoms
Donor
Levels
ValenceValenceband
H. Lüth Solid Surfaces, Interfaces
Tutorial September 2008 Barcelona_H. Kohlstedt53
,and Thin Films, p. 273, Springer 2001
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Schottky, too simple: S = 1Schottky, too simple: S 1
Bardeen, too pessimistic approach: S = 0
Heine´s approach : MIGS (Metal Induced Gap States)V H i Ph R 138 A 1689 (1965)V. Heine Phys. Rev. 138, A 1689 (1965).
Metal Vacuum
Metal Semiconductor
Metal Semiconductor
Tutorial September 2008 Barcelona_H. Kohlstedt54
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Measurement of the Slope Parameter S
1) Schottky: Clean limit
2) Bardeen: Surface states at Semic. Surface
3) H i M t l I d d G St t (MIGS)3) Heine: Metal Induced Gap States (MIGS)
4) Real Interface structure and defects are important
S = 0.08 (slope parameter)(from experiment)
Tutorial September 2008 Barcelona_H. Kohlstedt55
Mönch, Springer: Electronic Properties of Semiconductor Interfaces, 2001, p. 6
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Wavefunctions of...
Metal Vacuum
... a (clean) metal surface
Metal Semiconductor
... a metal-semiconductor interface
... a surface state
Vacuum Semiconductor
Tutorial September 2008 Barcelona_H. Kohlstedt56Sketch from:
W. Mönch, Electr. Prop. of Semicond. Interf., p. 8
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Extrinsic FactorsEVac
E
EFEF
Metal SemiconductorMetal Semiconductor
Reacted region
Interdiffuison region
Tutorial September 2008 Barcelona_H. Kohlstedt57
L. J. Brillson, Surf. Sci. 299/300, 909 (1994).
Nonmatching bonds, surface states, impurities etc.are important to undertand Schottky contacts
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The Metal Oxide Semiconductor Capacitor
MOS-Capacitor
Work functionGate metalSiO2
Work functionEnergy gapBand structure
Silicon (Si) Interface statesDefectsDevice fabricationDevice fabrication...
Why it took more than 30 years to realize a MOSFET?
...the MOS cap was a „hard nut“ - in preparation and in understanding!!
Tutorial September 2008 Barcelona_H. Kohlstedt58
...the MOS cap was a „hard nut in preparation and in understanding!!
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MOSFET and Interface Traps
Trap density:
Gate metal+ + + + + + + +
ap de s ty< 1012 /cm2/eVrequired
SiO - - TrapsSiO2
- --
- - -
Tutorial September 2008 Barcelona_H. Kohlstedt59
Silicon (Si)
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Complex Oxide Interfaces
F t
Ferroelectric
Metal
Ferroelectric
Ferromagnet
Metal Ferromagnet
Tutorial September 2008 Barcelona_H. Kohlstedt60
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ABO3 Complex Oxides (2 Examples)
Huge (remanent) surface charge SrRuO3: ConductorFerroelectric
Ba or Pb Sr
Ti
+P -P
O
Ru
Oc
Oa
PbZrxTi1-xO3
Tutorial September 2008 Barcelona_H. Kohlstedt
BaTiO3
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Ferroelectric Hysteresis
“1” Pr
BaTiO
Metal
P zatio
n
BaTiO3
Metal
P
E
Pol
ariz
Electric Field
Ec“0”
Electric Field
Pr = 10 – 80 µC/cm2
Ec = 50 – 300 kV/cm2Comparison:
1 l t / f tThin Film Capacitor: t = 100 nm
1 electron/per surface atom:1015/cm2 x 1.6 x 10-19 C =160 µC/cm2
Tutorial September 2008 Barcelona_H. Kohlstedt62VC = 0.5 V - 2 V strong interface
effects expected!!
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Metal-Ferroelectric Interfaces
Tutorial September 2008 Barcelona_H. Kohlstedt63
J. F. Scott, Ferroelectric Memories p. 81, Fig. 4.1
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Electrical Boundary Conditions
Screening by Electrons
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _Metal
0⇒DE0=⋅∫ dsE+ + + + + + + + + + + + + + + + + + + + +
EDP (only for
f t i !!)
0⇒DE0∫ dsE
perfect screening!!)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Metal
+ + + + + + + + + + + + + + + + + + + + +
Potential
x
Tutorial September 2008 Barcelona_H. Kohlstedt64P. Würfel and I. P. Batra , Ferroelectrics 12, 55 (1976).
J. Juncquera and Ph. Ghosez, Nature 422, 506 (2003).
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Layer Sequence of a Tunnel Junction
Top electrode(50 nm)
T l B iTunnel Barrier(1 nm – 3 nm)
Substrate
B ttBottom Electrode(50 nm)
Tutorial September 2008 Barcelona_H. Kohlstedt65
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Reaching the Tunneling Regime
Darrel Schlom & ChambersPenn State &Penn StateMBE grown oxidesJulio Rodriguez
&
SrRuO3S uO3
BaTiO3
21.5 nm2.1 nm
SrRuO380 nm
5 nm
Tutorial September 2008 Barcelona_H. Kohlstedt6620nm
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Tunneleffect
real realRe
φxikxeB=ΨBΨ k k xkreal
imaginary
realB
eBΨB xk xk xk
xikC
xeC=Ψ
x
Re AΨ
xikA
xeA −=Ψ
Transmission coefficientTransmission coefficient
⎪
⎪⎬⎫
⎪⎪⎨⎧−= ∫ dxxmCT
t
)(22exp φ
Tutorial September 2008 Barcelona_H. Kohlstedt67
⎪⎭⎬
⎪⎩⎨ ∫
0
)(ph
Frenkel, Phys. Rev. 36 (1930)
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Electron Tunneling across a Ferroelectric
H K hl t dt t l Ph R B 72 125341 (2005)
Tutorial September 2008 Barcelona_H. Kohlstedt68
H. Kohlstedt et al., Phys. Rev. B 72, 125341 (2005).E. Y. Tsymbal and H. Kohlstedt, Science 313, 181 (2006).
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Superconducting -, Magnetic-, and Ferroelectric Tunnel Junctions
Dielectric Barrier Density of states effects
Superconductor Superconductor Magnet Magnet
[ ]dEEfeVEfEneVEnETAeVI )()()()()(2)( 21 −−⋅−= ∫∞
h
π∫∞−h
Metal Metal
Ferroelectric tunnel junction:
Cooperative phenomenon
Tutorial September 2008 Barcelona_H. Kohlstedt69Ferroelectric Barrier
located in the barrier !
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Alternative Screening Mechanism I
Fong, et al., Phys. Rev. B 71, 144112 (2005).Ionic Screening
Tutorial September 2008 Barcelona_H. Kohlstedt70Theoretically: G. Gerra et al., PRL (2006).
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Rearrangements of Surface Atoms
Perfect/truncated bulkFew examples:
Relaxation Reconstruction Missing row reconstruction
c2
c1
cbulk
Tutorial September 2008 Barcelona_H. Kohlstedt71
a
From: H. Lüth, Surfaces and Interfaces of Solids, Springer, p. 79
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Alternative Screening Mechanism IImetal ferroelectric
Th F i i dThomas-Fermi screening andKretschmer-Binder effect
CTF CKB
B d h ti b fBond charge compensation by freecarriers in the ferroelectric
E t i f th i i l i tiExtension of the ionic polarizationinto the metal; Ionic distortion also in the metal
Tutorial September 2008 Barcelona_H. Kohlstedt72
Sketch taken from G. Gerra et al.,PRL 96. 107603 (2006). Fig.1
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Alternative Screening Mechanism
Ionic Screening
Fong, et al., Phys. Rev. B 71, 144112 (2005).
G. Gerra et al., PRL (2006).
1.5
2.0Electron Wave Interference
0.5
1.0
ER
GY
(eV
) M. Indlekofer and H. KohlstedtEurophysics Lett. 72, 282 (2005).Friedel Oscillations at interface;
-1.0
-0.5
0.0
EN
Tutorial September 2008 Barcelona_H. Kohlstedt
5 10 15 20 251.0
z (nm)
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Pt/BaTiO3/Pt Tunnel Junctions
Tutorial September 2008 Barcelona_H. Kohlstedt74
J. P. Velev et al., PRL 98, 137201 (2007)
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F t
Ferroelectric
Ferromagnet
Ferromagnet
Tutorial September 2008 Barcelona_H. Kohlstedt75
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Magnetoelectric Interface Effect
Fe/BaTiO3
Interface between a ferromagnet and a ferroelectric
PPa ferromagnet and a ferroelectric
Top interface
DO
SMinority-spin charge density
Bottom interface
Tutorial September 2008 Barcelona_H. Kohlstedt76C.-G. Duan, S.S. Jaswal and E. Y. Tsymbal,
PRL 97, 047201 (2006).
EF
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Multiferroic Materials: BiFeO3, BiMnO3 etc.Multiferroic Heterostructures: FE/FM/FE/FM/….
+ - + -
E+ - + -
P
MN S
ε M
H
ε
N. A. Spaldin and M. Fiebig, Science 309, 391 (2005). Sketch taken from Fig.1.
Hσ
Tutorial September 2008 Barcelona_H. Kohlstedt77
W. Eerenstein, N. D. Mathur and J. F. ScottNature, 442, 759 (2006) and references therein
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Fe/BaTiO3/Fe Tunnel Junctions
Tutorial September 2008 Barcelona_H. Kohlstedt78
Julian P. Velev, et al., JOURNAL OF APPLIED PHYSICS 103, 07A701 2008
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J.F. Scott, Nat. Mat. 6, 256 (2007).Mat Nat 6 296 (2007)
Tutorial September 2008 Barcelona_H. Kohlstedt79
J.F. Scott, Nat. Mat. 6, 256 (2007).Mat. Nat. 6, 296 (2007).
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Travelers undergo a lot
M l l d Ph El t Ph
(Inelastic) Electron Tunneling Spectroscopy
Molecule and Phonon Spectroscopy
Electron-Phonon Coupling α2 (ω,k)Magnons
P. Balk, JAP 1991 J. S. Moodera, PRL 1998 E. L. Wolf, PRB 1985,
n-Si/SiO2/Al Co/Al2O3/Ni80Fe20 Nb/MgO/Ag
Tutorial September 2008 Barcelona_H. Kohlstedt80
Tunneling electrons are extremely sensitive to barrier and interface excitations!
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An optimistic Outlook
Pyroelectric
Multiferroic Tunnel Junctions
P t- - -
FerroelectricAnti-ferroelectric
PyroelectricPiezoelectricDielectric
Paramagnet(Anti)-Ferromagnet
Superconductor
+ + +
- - -Multiferroic (Insulator)(Tunnel Barrier)
P, M
+ + +
(Tunnel Barrier)
MagneticAnti-ferromagnetic
Examples: -Cross correlation between magnetic and ferroelectric (piezoelectric) properties
Superconductor-Ferroelectric-Superconductor junction:- Joesphson coupling and screening charge?- Josephson (quasi particle) current and resistive state of the barrier?
Tutorial September 2008 Barcelona_H. Kohlstedt81
Josephson (quasi particle) current and resistive state of the barrier?-Magnet-Ferroelectric-Magnet Junctions:-Spin dependent screening?
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A few Milestones in Electron Tunneling
2010Experiments and theory on ferroelectric and multiferroictunnel junctionss
1990 Superconducting HTc tunnel junctions (not successful)First all-oxide magnetic tunnel junctiontunnel junctions
Oxi
des
Magnetic Tunnel Junctions
Supe co duct g c tu e ju ct o s ( ot success u )
1970
Superconducting Tunnel Junctions (LTc)
Magnetic Tunnel Junctions
Magnetic/Superconducting Hybrids, Spin Polarization
s
1950
Superconducting Tunnel Junctions (LTc)
Met
als
1950
Tutorial September 2008 Barcelona_H. Kohlstedt82
1930 Theory and first experiments: Metal/Barrier/Metal
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Literature
H. Lüth, Springer: Surfaces and Interfaces of Solids, 2001
Zangwill Cambridge: Physics at Surfaces 1988Zangwill, Cambridge: Physics at Surfaces, 1988
Desjonqueres, Springer: Concepts in Surface Physics
Feldmann/Mayer, North Holland: Fundamentals of Surface and Thin Film Analysis
Rudden/Wilson, Wiley: Elements of Solid State Physics
Mönch, Springer: Electronic Properties of Semiconductor Interfaces, p g p
H. Ibach and H. Lüth: Introd. to Solid State Physics, 1991Springer
J. F.Scott, Springer: Ferroelectric Memories, 2000
Tutorial September 2008 Barcelona_H. Kohlstedt83
S. M. Sze, Wiley, Phys. of Semicond. Devices, 1981
pdf file: [email protected]