Part I Theoretical Aspects
Theoretical Aspects of Phase Transitions in Ferroelectric Thin
Films
Yoshihiro Ishibashi ............................................. 3
1 Introduction ................................................. 3
2 The Tilley-Zeks Model ........................................ 4
3 Transition Temperature and Polarization Profile .............. 5
3.1 The Case of Zero Extrapolation Length (δ+ = δ- = 0) ...... 6
3.2 The Case of Positive Extrapolation Length
(δ+ = δ- = δ > 0) ........................................ 9
3.3 The Case of Negative Extrapolation Length
(δ+ = δ- = δ < 0) ....................................... 12
4 Asymmetric Films ............................................ 14
4.1 The Positive-Positive Case (δ+ > 0, δ- > 0) .............. 15
4.2 The Negative-Negative Case (δ+ < 0, δ- < 0) .............. 15
4.3 The Mixed Case .......................................... 15
4.3.1 The Case of |δ-| < |δ+| ............................ 16
4.3.2 The Case of |δ-| > |δ+| ............................ 16
5 Notes on Exact and Approximate Polarization Profiles ........ 16
6 Concluding Remarks .......................................... 19
References ..................................................... 20
Part II Preparation and Characterization of Ferroelectric
Thin Films
Theoretical Aspects of Phase Transitions in Ferroelectric
Thin Films
Shin-ichi Hirano, Takashi Hayashi, Wataru Sakamoto,
Koichi Kikuta, Toshinobu Yogo .................................. 25
1 Introduction ................................................ 25
1.1 The Chemical Solution Deposition Process ................ 26
1.2 Representative Ferroelectric Thin Films for Memory
Devices ................................................. 28
1.3 Layer-Structured Bi4Ti3O12-Based Thin Films .............. 28
2 Rare-Earth-Ion-Modified Bi4Ti3O12 Thin Films ................. 29
2.1 Chemical Processing of (Bi,R)4Ti3O12 Precursor
Solutions, Powders and Thin Films ....................... 29
2.2 Crystallization and Pyrolysis Behavior of (Bi,R)4Ti3О12
Precursors .............................................. 31
2.3 Crystallization of (Bi,R)4Ti3O12 Thin Films .............. 33
2.4 Surface Morphologies of (Bi,R)4Ti3O12 Films .............. 35
2.5 Phase Transition and Ferroelectric Properties ........... 36
2.6 Effect of Nd Content on Nd-Modified BIT (BNT) Thin
Films ................................................... 39
2.7 Effect of Processing Temperature on Nd-Modified BIT
(BNT) Thin Films ........................................ 41
3 Ge-Doped (Bi,Nd)4Ti3O12 Thin Films ........................... 43
3.1 Fabrication of (Bi,Nd)4(Ti,Ge)3O12 Films ................. 43
3.2 Microstructure and Electrical Properties of
(Bi,Nd)4Ti3O12 Films ..................................... 45
4 UV Processing of (Bi,Nd)4Ti3O12
(BNT) Thin Films ............................................ 46
4.1 Changes in the Chemical Bonding of Excimer-UV-
Irradiated BNT Precursor Films .......................... 47
4.2 Effect of UV Light Irradiation on the Crystal
Orientation of the Resultant Thin Films ................. 48
4.3 Surface Morphology of UV-Light-Irradiated BNT Thin
Films ................................................... 50
4.4 Ferroelectric Properties of UV-Irradiated BNT Thin
Films ................................................... 51
4.5 Fatigue and Leakage Current Properties of
UV-Irradiated BNT Thin Films ............................ 54
References ..................................................... 56
Pb-Based Ferroelectric Thin Films Prepared by MOCVD
Masaru Shimizu, Hironori Fujisawa, Hirohiko Niu ................ 59
1 Introduction ................................................ 59
2 Experimental Procedure ...................................... 61
3 Microscopic Observation of the Initial Growth Stages of
PbTiO3 and PZT Thin Films on Various Substrates ............. 62
3.1 Growth Process of PbTiO3 and PZT Thin Films on
Polycrystalline Pt/SiO2/Si .............................. 62
3.2 Growth Process of PZT Thin Films on SrTiO3 Single
Crystals ................................................ 64
3.3 Growth Process of PZT Thin Films on Epitaxial
SrRuO3/SrTiO3 ........................................... 65
4 Epitaxial PZT Ultrathin Films ............................... 67
4.1 Preparation of PZT Ultrathin Films on SrRuO3/SrTiO3 ..... 67
4.2 Ferroelectric Properties of PZT Ultrathin Films ......... 67
5 Self-Assembled PbTiO3 and PZT Nanostructures and Their
Ferroelectric Properties .................................... 71
5.1 Preparation of Self-Assembled PbTiO3 and PZT
Nanostructures on Various Substrates .................... 71
5.2 Piezoelectric and Ferroelectric Properties of PbTiO3
Nanostructures .......................................... 72
References ..................................................... 74
Spontaneous Polarization and Crystal Orientation Control of
MOCVD PZT and Bi4Ti3O12-Based Films
Hiroshi Funakubo ............................................... 77
1 Introduction ................................................ 77
2 Spontaneous Polarization .................................... 77
2.1 PZT Films ............................................... 78
2.2 Bi4Ti3O12-Based Films .................................... 80
3 Remanent Polarization of Polycrystalline Ferroelectric
Films Prepared on Si Substrates ............................. 83
3.1 PZT Films ............................................... 83
3.2 Bi4Ti3O12-Based Films .................................... 85
3.3 Low-Temperature Deposition .............................. 86
3.4 PZT Films ............................................... 87
3.5 Bi4Ti3O12-Based Films .................................... 87
References ..................................................... 88
Rhombohedral PZT Thin Films Prepared by Sputtering
Masatoshi Adachi ............................................... 91
1 Introduction ................................................ 91
2 Experimental Procedures ..................................... 92
3 PZT Films on (Pb,La)TiO3 (PLT)/Pt/Ti/SiO2/Si and
Ir/SiO2/Si .................................................. 93
4 Rhombohedral PZT on (111) Ir/(111) SrTiO3 and (100)
Ir/(100) SrTiO3 Substrates ................................. 101
References .................................................... 103
Scanning Nonlinear Dielectric Microscopy
Yasuo Cho ..................................................... 105
1 Introduction ............................................... 105
2 Principle and Theory of SNDM ............................... 106
2.1 Nonlinear Dielectric Imaging with Subnanometer
Resolution ............................................. 107
2.2 Comparison between SNDM Imaging and Piezoresponse
Imaging ................................................ 111
3 Higher-Order Nonlinear Dielectric Microscopy ............... 112
3.1 Theory of Higher-Order Nonlinear Dielectric
Microscopy ............................................. 112
3.2 Experimental Details of Higher-Order Nonlinear
Dielectric Microscopy .................................. 113
4 Three-Dimensional Measurement Technique .................... 115
4.1 Principle and Measurement System ....................... 116
4.2 Experimental Results ................................... 117
5 Tb/in2 Ferroelectric Data Storage Based on SNDM ............ 118
References .................................................... 123
Part III Relaxors
Analysis of Ferroelectricity and Enhanced Piezoelectricity
near the Morphotropic Phase Boundary
Makoto Iwata, Yoshihiro Ishibashi ............................. 127
1 Introduction ............................................... 127
2 Free Energy and Phase Diagram .............................. 128
3 Dielectric Constants, Elastic Constants and
Electromechanical Coupling Constants ....................... 131
4 Polarization Reversal ...................................... 134
5 Enhanced Piezoelectricity Under an Oblique Field ........... 140
6 Magnetostrictive Alloys of Rare-Earth Fe2 Compounds ........ 144
References .................................................... 145
Correlation Between Domain Structures and Dielectric
Properties in Single Crystals of Ferroelectric Solid
Solutions
Naohiko Yasuda ................................................ 147
1 Introduction ............................................... 147
2 Single-Crystal Preparation ................................. 148
2.1 Flux Method ............................................ 148
2.2 Solution Bridgman Method ............................... 149
3 Measurement ................................................ 150
4 Domain Structures in the PIN-PT Solid Solution ............. 150
4.1 Temperature Dependence of the Permittivity, Domain
Structure and Birefringence ............................ 150
4.2 The Effect of a dc Bias Field on the Domain
Structure .............................................. 152
5 Domain Structures in a (001) Plate of a PMN-PT Solid
Solution ................................................... 156
References .................................................... 158
Relaxor Superlattices: Artificial Control of the Ordered-
Disordered State of B-Site Ions in Perovskites
IIitoshi Tabata ............................................... 161
1 Relaxor Behavior in Perovskite-Type Dielectric Compounds ... 161
1.1 Introduction ........................................... 161
1.2 Experimental Procedure ................................. 162
1.3 Results and Discussion ................................. 163
1.4 Conclusions ............................................ 167
2 Artificial Control of the Ordered/Disordered State of
b-Site Ions in Ba(Zr,Ti)O3 by a Superlattice Technique ..... 167
2.1 Introduction ........................................... 167
2.2 Experimental ........................................... 168
2.3 Results and Discussion ................................. 170
References .................................................... 172
Part IV Ferroelectric-Insulator-Semiconductor Junctions
Physics of Ferroelectric Interfaces:
An Attempt at Nanoferroelectric Physics
Yukio Watanabe ................................................ 177
1 Spontaneous Polarization and the Ferroelectric Surface ..... 177
2 Electric Field in and Arising from a Ferroelectric ......... 178
2.1 Ferroelectric Covered by Metal (M/F) ................... 178
2.2 Ferroelectric Covered by Semiconductor (S/F) ........... 179
2.3 Ferroelectric Covered by Insulator or Nothing (I/F),
and Depolarization Field ............................... 179
2.4 Surface Relaxation Modeling of I/F Structure and
Generalization ......................................... 180
3 Ferroelectric Field Effect Devices ......................... 181
4 Domains, Depolarization Instability, and Memory
Retention .................................................. 181
5 Epitaxial Strain and the Surface Relaxation ∇P Effect ..... 183
5.1 Epitaxial Strain vs. Depolarization Instability ........ 183
5.2 The Surface Relaxation ∇P Effect Can Be Unimportant ... 184
6 Finite Band Gap Energy and Redefinition of "Insulator" ..... 185
6.1 Reexamination of the Depolarization Field .............. 185
6.2 Relaxation Semiconductors .............................. 186
6.3 Insulator Under Static Field ........................... 186
6.4 Ferroelectric Under Static Field ....................... 186
6.5 The Natural Choice of a Ferroelectric .................. 187
7 Modeling of F/l/S Interfaces ............................... 188
7.1 Mathematical Formulation ............................... 188
7.2 Approximations ......................................... 191
8 Comparison with Experiments: Leakage Current and
Dynamics ................................................... 191
8.1 Numerical Results for Typical Structures ............... 191
8.2 Retention and Leakage Current .......................... 192
8.3 Contradiction and Solution: Miller-McWhorter Theory .... 193
9 Intrinsic 2D Electron Layers ............................... 195
10 Ferroelectric Coupled to Free Electrons: Ferroelectric 2D
Metal ...................................................... 196
11 Concluding Remarks ......................................... 196
References .................................................... 196
Preparation and Properties of Ferroelectric—Insulator-
Semiconductor Junctions Using YMnO3 Thin Films
Norifumi Fujimura, Takeshi Yoshimura .......................... 199
1 Introduction ................................................ 199
2 Material Design of Ferroelectric and Insulator Layers for
MF(I)S Capacitors ........................................... 200
3 Fabrication of YMnO3 Epitaxial Films ........................ 204
4 Fabrication and Properties of Y2O3 Films on Si ............... 206
5 Fabrication of YMnO3/Y2O3/Si Capacitors ...................... 208
6 Investigation of Retention Characteristics of YMnO3/Y2O3/Si
Capacitors .................................................. 210
7 Influence of Leakage Current on the Retention
Characteristics of YMnO3/Y2O3/Si Capacitors .................. 211
References .................................................... 217
Improvement of Memory Retention in Metal-Ferroelectric-
Insulator-Semiconductor (MFIS) Structures
Masanori Okuyama, Minora Noda ................................. 219
1 Introduction ................................................ 220
2 Theoretical Analysis of Memory Retention in MFIS
Structures .................................................. 220
2.1 Capacitance Retention Characteristics ................... 220
2.2 Theoretical Studies of Band Profile and Retention
Degradation of MFIS Capacitors .......................... 222
2.2.1 Construction of MFIS Model and Analysis Method .... 222
2.2.2 Calculated Band Diagrams .......................... 224
2.3 Effects of Currents Through the Ferroelectric and
Insulator Layers on Retention Characteristics of MFIS
Structures .............................................. 225
2.3.1 Effects of Schottky Current Through Insulator
Layer ............................................. 225
2.3.2 Effects of Schottky Current Through
Ferroelectric Layer ............................... 226
2.3.3 Effects of Absorption Current in Ferroelectric
Layer ............................................. 227
2.3.4 Discussion of Current Reduction ................... 228
3 Advanced Structures to Improve Retention Time ............... 228
3.1 Enhancement of Barrier Height ........................... 228
3.2 Insertion of Ultrathin Insulator Layer Between Metal
and Ferroelectric Layers ................................ 228
3.3 High-k; Insulator Layer Instead of SiO2 Film ............ 230
4 Experimental Improvement of Retention Time by O2
Annealing ................................................... 231
4.1 Effect of O2 Annealing on Physical Properties of SBT
Thin Films on (111) Pt/Ti/SiO2/Si Substrates ............ 231
4.2 Polarization Retention Characteristics of Pt/SBT/Pt
Capacitors .............................................. 231
4.3 Current Conduction in SBT Films ......................... 232
4.4 Retention Improvement of MFIS Structures by O2
Annealing ............................................... 233
4.5 More Improvement by Rapid Thermal Annealing ............. 234
5 Photoyield Spectroscopic Studies on SBT Thin Films .......... 235
5.1 Principle of Photoyield Spectroscopy of SBT Films ....... 235
5.2 Effects of O2 Annealing on SBT Thin Films Studied by
UV-PYS .................................................. 236
References .................................................... 238
Index ......................................................... 241
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