List of contributors ........................................... xv
PART I FUNDAMENTALS
1 A brief introduction to strongly correlated electronic
materials .................................................... 3
E. DAGOTTO and Y. TOKURA
1.1 Motivation .............................................. 3
1.2 Introduction ............................................ 3
1.3 Why correlated electrons? ............................... 5
1.4 Control of correlated electrons in complex oxides ....... 6
1.5 Ordering of charge, spin, and orbital degrees of
freedom ................................................ 11
1.6 Model Hamiltonians ..................................... 14
1.7 Intrinsically inhomogeneous states ..................... 15
1.8 Giant responses in correlated electron systems ......... 18
1.9 Importance of quenched disorder and strain ............. 24
1.10 Outlook for correlated-electron technology:
spintronics, double perovskites, multiferroics,
orbitronics, resistance switching ...................... 28
1.11 Conclusions ............................................ 32
Acknowledgments ............................................. 32
References .................................................. 32
2 Magnetoelectric coupling and multiferroic materials ......... 38
Gustau CATALAN and James F. SCOTT
2.1 Introduction: magnetoelectric coupling and
multiferroic materials ................................. 38
2.2 Magnetoelectric coupling ............................... 40
2.2.1 Linear coupling: Dzyaloshinskii-Moriya effect,
electrically induced spin canting, and
Shtrikman limit ................................. 41
2.2.2 Biquadratic (strain mediated) coupling .......... 42
2.2.3 Perovskite oxides: why are they seldom
multiferroic? ................................... 43
2.3 Magnetoelectric multiferroics .......................... 44
2.3.1 Perovskites with ferroelectricity caused by
lone-pair polarization: BiFeO3 .................. 44
2.3.2 Oxides with ferroelectricity caused by spins
spirals: ТbМnО3, TbMn2O5 ........................ 46
2.3.3 Hexagonal multiferroics: YMnО3 .................. 46
2.3.4 Unconfirmed oxide multiferroics: RNiO3 (R =
rare earth or Bi) ............................... 47
2.3.5 Magnetoelectric relaxors ........................ 48
2.3.6 Ferromagnetic ferroelectric fluorides ........... 51
2.3.7 Ferrimagnetic ferroelectrics .................... 55
Appendix 2.1 Magnetoelectric measurements ................... 57
Appendix 2.2 Critical exponents in isostructural phase
transitions ............................................ 59
References .................................................. 61
PART II OXIDE FILMS AND INTERFACES: GROWTH AND CHARACTERIZATION
3 Synthesis of epitaxial multiferroic oxide thin films ........ 73
Thomas TYBELL and Chang-Beom EOM
3.1 Introduction ........................................... 73
3.2 Substrates ............................................. 75
3.2.1 Strain, orientation, and symmetry control by
choice of substrate ............................. 75
3.2.2 Substrate termination and surface quality ....... 77
3.3 Strain engineering as a tool for controlling
functional oxide thin films ............................ 79
3.3.1 SrRuO3 - a case study of strain engineering ..... 80
3.3.2 Effect of defects ............................... 86
3.4 Vicinal control of functional properties ............... 86
3.4.1 SrRuO3 - a case study of vicinal control of
orthorhombic domain structure ................... 87
3.4.2 BiFeO3 - domain control of a prototype
rhombohedral material by substrate miscut ....... 88
3.4.3 Mono-domain samples—enabling fundamental
studies and enhanced properties of BiFeO3 ....... 91
3.5 Conclusions ............................................ 95
Acknowledgments ............................................. 96
References .................................................. 96
4 Synchrotron X-ray scattering studies of oxide
heterostructures ............................................ 99
Dillon D. FONG
4.1 Introduction ........................................... 99
4.2 Surface X-ray diffraction ............................. 100
4.3 Resonant scattering ................................... 105
4.4 Anisotropic effects ................................... 115
4.5 Summary ............................................... 118
Acknowledgments ............................................ 118
References ................................................. 118
5 Scanning transmission electron microscopy of oxides ........ 123
M. VARELA, C. LEON, J. SANTAMARIA, and S.J. PENNYCOOK
5.1 Introduction to STEM .................................. 123
5.2 STEM imaging .......................................... 128
5.2.1 Probe formation ................................ 129
5.2.2 Time reversal symmetry in electron microscopy .. 130
5.2.3 Image simulation ............................... 131
5.3 Mapping materials properties through EELS fine
structure ............................................. 135
5.4 Applications: interfaces in manganite/cuprate
heterostructures ...................................... 138
5.5 Summary ............................................... 150
Acknowledgments ............................................ 150
References ................................................. 151
6 Advanced modes of piezoresponse force microscopy for
ferroelectric nanostructures ............................... 157
A. GRUVERMAN
6.1 Introduction .......................................... 157
6.2 Ferroelectric structures and size effects ............. 158
6.3 Advanced modes of PFM ................................. 162
6.3.1 Resonance-enhanced PFM: static domain imaging .. 162
6.3.2 Stroboscopic PFM: domain switching dynamics .... 165
6.3.3 PFM Spectroscopy: spatial variability of
switching parameters ........................... 170
6.4 Summary ............................................... 174
Acknowledgments ............................................ 175
References ................................................. 175
PART III OXIDE FILMS AND INTERFACES: FUNCTIONAL PROPERTIES
7 General considerations of the electrostatic boundary
conditions in oxide heterostructures ....................... 183
Takuya HIGUCHI and Harold Y. HWANG
7.1 Introduction .......................................... 183
7.2 The polar discontinuity picture ....................... 185
7.2.1 Stability of ionic crystal surfaces ............ 185
7.2.2 Stability of covalent surfaces ................. 187
7.2.3 Polar semiconductor interfaces ................. 188
7.3 Metallic conductivity between two insulators .......... 192
7.3.1 The polar discontinuity scenario ............... 193
7.3.2 Oxygen vacancy formation during growth ......... 194
7.3.3 Intermixing and local bonding at the
interface ...................................... 194
7.3.4 Reconciling the various mechanisms ............. 196
7.4 The local charge neutrality picture ................... 196
7.4.1 Unit-cells in ionic crystals ................... 196
7.4.2 LaAlO3/SrTiO3 in the local charge neutrality
picture ........................................ 198
7.4.3 Coupling of polar discontinuities .............. 199
7.4.4 Modulation doping by a proximate polar
discontinuity .................................. 201
7.4.5 Advantages of the local charge neutrality
picture ........................................ 202
7.5 Equivalence of the two pictures ....................... 203
7.5.1 Gauss' law for infinite crystals ............... 203
7.5.2 Gauss' law for finite crystals ................. 204
7.6 Further discussions ................................... 205
7.6.1 Effect of interdiffusion ....................... 205
7.6.2 Role of correlation effects .................... 207
7.6.3 Quadrupolar discontinuity ...................... 207
7.7 Summary ............................................... 209
Acknowledgments ............................................ 210
References ................................................. 210
8 Strongly correlated heterostructures ....................... 214
Satoshi OKAMOTO
8.1 Introduction .......................................... 214
8.2 Theoretical description ............................... 218
8.2.1 Model .......................................... 218
8.2.2 Layer-extension of dynamical-mean-field
theory ......................................... 222
8.2.3 Auxiliary particle methods...................... 225
8.3 Mott-insulator/band-insulator heterostructures ........ 226
8.3.1 Lattice relaxation and charge redistribution ... 226
8.3.2 Mott physics ................................... 229
8.4 Superlattices of under-doped-cuprate/over-doped-
cuprate ............................................... 232
8.5 Other directions ...................................... 236
8.5.1 Surface magnetism of double-exchange
manganites ..................................... 237
8.5.2 Transport through two-terminal strongly
correlated heterostructures .................... 240
8.6 Summary ............................................... 243
Acknowledgments ............................................ 245
References ................................................. 245
9 Manganite multilayers ...................................... 254
Anand BHATTACHARYA, Shuai DONG, and Rong YU
9.1 Motivation ............................................ 254
9.2 Introduction to manganites ............................ 255
9.3 Theoretical description of manganite multilayers ...... 256
9.4 Synthesis and structure of manganite multilayers ...... 259
9.5 Recent progress on manganite multilayers .............. 262
9.5.1 Phase transitions and orbital order driven
by strain ...................................... 262
9.5.2 Charge transfer and spin-polarized two-
dimensional electron gas ....................... 265
9.5.3 A-site ordering in short-period superlattices .. 267
9.5.4 Tuning between ferromagnetism and
antiferromagnetism ............................. 273
9.5.5 Interfacial magnetism .......................... 276
9.5.6 Metal-insulator transitions .................... 278
9.5.7 Half-manganite heterostructures: band lineup
and magnetic interactions at interfaces ........ 285
9.6 Conclusions and outlook ............................... 290
Acknowledgments ............................................ 291
References ................................................. 291
10 Thermoelectric oxides: films and heterostructures .......... 296
Hiromichi OHTA and Kunihito KOUMOTO
10.1 Introduction .......................................... 296
10.2 p-type layered cobalt oxide: Са3Со4O9 films ........... 297
10.3 Heavily electron doped БгТЮз films .................... 300
10.4 Two-dimensional electron gas .......................... 306
10.5 Field effect thermopower modulation ................... 309
10.6 Summary ............................................... 312
References ................................................. 312
PART IV APPLICATIONS
11 High-k gate dielectrics for advanced CMOS .................. 319
Suman DATTA and Darrell G. SCHLOM
11.1 Introduction .......................................... 319
11.2 High-k dielectric materials ........................... 322
11.3 Metal-gate electrodes ................................. 323
11.3.1 Poly-depletion elimination ..................... 323
11.3.2 Interfacial layer control ...................... 323
11.3.3 High-x: phonon screening ....................... 324
11.3.4 Metal gates with "correct" work function ....... 325
11.4 High-k/metal-gate silicon FETs ........................ 326
11.4.1 Integration .................................... 326
11.4.2 Devices ........................................ 329
11.4.3 Reliability .................................... 329
11.5 High-k/metal-gate nonsilicon FETs ..................... 330
11.5.1 Integration .................................... 330
11.5.2 Devices and characterization ................... 331
Acknowledgments ............................................ 334
References ................................................. 335
12 FeFET and ferroelectric random access memories ............. 340
Hiroshi ISHIWARA
12.1 Overview of ferroelectric random access memories
(FeRAMs) .............................................. 340
12.2 Ferroelectric films used for FeRAMs ................... 342
12.2.1 Properties necessary for FeRAMs ................ 342
12.2.2 Pb(Zr,Ti)O3 and Bi-layer structured
ferroelectrics ................................. 344
12.2.3 Novel ferroelectric films with large remanent
polarization ................................... 346
12.3 Cell structure and operation principle of capacitor-
type FeRAMs ........................................... 349
12.3.1 Cell structure of 1T1C(2T2C)-type FeRAMs ....... 349
12.3.2 Operation principle of 1T1C(2T2C)-type FeRAMs .. 352
12.3.3 Other capacitor-type FeRAMs .................... 354
12.4 Cell structure and operation principle of FET-type
FeRAMs ................................................ 357
12.4.1 Optimization of FeFET structure ................ 357
12.4.2 Data retention characteristics of FeFETs ....... 358
12.4.3 Cell array structures .......................... 360
References ................................................. 362
13 LaAlO3/SrTiO3-based device concepts ........................ 364
Daniela F. BOGORIN, Patrick IRVIN, Cheng CEN, and Jeremy
LEVY
13.1 Introduction .......................................... 364
13.1.1 Semiconductor 2DEGs ............................ 365
13.1.2 2DEG at LaAlO3/SrTiO3 interface ................ 365
13.1.3 Polar catastrophe model ........................ 365
13.1.4 Metal-insulator transition in LaAlO3/SrTiO3 .... 366
13.1.5 Inconsistencies with the polar catastrophe model 367
13.2 Field-effect devices .................................. 368
13.2.1 SrTiO3-based channels .......................... 368
13.2.2 Electrical gating of LaAlO3/SrTiO3 structures .. 368
13.2.3 LaAlO3/SrTiO3-based field-effect devices ....... 370
13.3 Reconfigurable nanoscale devices ...................... 370
13.3.1 Nanoscale writing and erasing .................. 371
13.3.2 "Water cycle" .................................. 372
13.3.3 LaAlO3/SrTiO3 as a floating-gate transistor
network ........................................ 373
13.3.4 Quasi-0D structures ............................ 375
13.3.5 Designer potential barriers .................... 375
13.3.6 SketchFET ...................................... 376
13.3.7 Nanoscale photodetectors ....................... 378
13.3.8 Integration of LaAlO3/SrTiO3 with silicon ...... 379
13.4 Future prospects ...................................... 381
13.4.1 Room-temperature devices ....................... 382
13.4.2 Information processing ......................... 382
13.4.3 Spintronics .................................... 382
13.4.4 Quantum Hall regime ............................ 383
13.4.5 Superconducting devices ........................ 383
13.4.6 Solid-state Hubbard simulators ................. 383
References ................................................. 384
Index ......................................................... 389
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