Foreword	5
	Preface	8
	Contents	10
	Abbreviations	17
	1. History of Phase Change Memories	21
	1.1 The Discovery of Phase Change Materials	21
	1.2 Early Electronic Computers and Memory Systems	22
	1.3 Pioneers in Phase Change Memory	24
	1.4 Early Attempts with Phase Change Memory	29
	1.5 Rebirth of Phase Change Memory	30
	References	34
	Part I:Material Science: Theoryand Experiment	35
	2. Density Functional Theory Calculations for Phase Change Materials	36
	2.1 Introduction	36
	2.2 The Theorem of Hohenberg and Kohn	37
	2.3 The Kohn-Sham Equation	39
	2.4 The Local Density Approximation	41
	2.5 Beyond Density Functional Theory	42
	2.6 Application of DFT in the Field of Phase Change Materials	43
	2.6.1 Structure Determination	44
	2.6.2 Electronic Properties	48
	References	55
	3. Nature of Glasses	58
	3.1 Introduction	58
	3.2 Thermodynamics of the Glass Transition	60
	3.3 Glass Transition from Dynamics	62
	3.4 Glass Forming Tendency	63
	3.4.1 Compositional Trends of the Glass TransitionTemperature	65
	3.5 Calorimetric Measurement of the Glass Transition Temperature and Related Thermal Properties	67
	3.6 Three Generic Classifications of Glasses and Glass Transitions	70
	3.7 Elastic Phases in Ionic and Super-ionic Glasses	73
	3.8 Ideal Glasses and Self-organization of Networks	73
	3.9 Does the View Below the Glass Transition Temperature Correlate with the View above the Glass Transition Temperature?	75
	3. 10 Glass Formation in Hydrogen Bonded Networks	76
	3.11 Epilogue	78
	References	78
	4. Structure of Amorphous Ge-Sb-Te Solids	82
	4.1 Introduction	82
	4.2 Structural Order in Amorphous Materials	83
	4.2.1 Short-range Order	83
	4.2.2 Medium-range Order	84
	4.2.3 Long-range Structure	85
	4.3 Experimental Structural Probes	86
	4.4 Structural Modeling	87
	4.5 The Structure of Amorphous Phase-change Materials	88
	4.5.1 Experimental Studies	88
	4.5.2 Simulational Studies	91
	4.6 Summary	97
	References	98
	5. Experimental Methods for Material Selection in Phase-change Recording	100
	5.1 Introduction	100
	5.2 Reversible Switching	101
	5.3 Phase-change Materials	103
	5.3.1 Crystallization by Nucleation and Growth	105
	5.3.2 Crystallization Dominated by Crystal Growth	107
	5.4 Archival Life Stability	108
	5.5 Crystallization Rate	110
	5.6 Material Optimization	112
	5.7 Outlook	116
	References	117
	6. Scaling Properties of Phase Change Materials	118
	6.1 Introduction	118
	6.2 Thin Films of Phase Change Materials	119
	6.2.1 Crystallization Temperature as a Function of Film Thickness	120
	6.2.2 Crystallization Rate as a Function of Film Thickness	124
	6.2.3 Change in Optical Constants and Electrical and Thermal Parameters as a Function of Film Thickness	127
	6.2.4 Limits of Storage Density in Thin Films	128
	6.3 Phase Change Nanowires	130
	6.4 Phase Change Nanoparticles	133
	6.5 Scaling in Time – Switching Speed of Phase Change Materials	137
	References	139
	7. Crystallization Kinetics	144
	7.1 Theory	144
	7.1.1 Homogeneous Crystal Nucleation	144
	7.1.1.1 Thermodynamics of Cluster Formation (Gibbs, 1878)	145
	7.1.1.2 Model Based on Equilibrium Distribution of Clusters (Volmer and Weber, 1926)	146
	7.1.1.3 Steady State Model (Becker and Döring, 1935)	147
	7.1.1.4 The Kinetic Pre-factor of the Nucleation Rate (Turnbull and Fisher, 1949)	148
	7.1.2 Heterogeneous Crystal Nucleation	152
	7.1.3 Crystal Growth	154
	7.1.3.1 Interface-controlled Growth	155
	7.1.3.2 Growth Controlled by Long-range Diffusion	156
	7.2 Measurements	157
	7.2.1 Crystallization Parameters Around the Glass Transition Temperature	157
	7.2.2 Crystallization Parameters Close to the Melting Temperature	161
	References	164
	8. Short and Long-Range Order in Phase Change Materials	168
	8.1 Historical Background	168
	8.1.1 Glass Formation Process	169
	8.2 Long-Range Order	170
	8.2.1 GeTe	171
	8.2.2 Ge-Sb-Te Alloys	173
	8.2.2.1 Metastable Ge-Sb-Te Alloys	173
	8.2.2.2 High-Pressure Effects on Metastable Ge-Sb-Te Alloys	175
	8.2.2.3 Ge-Sb-Te Equilibrium Structures	176
	8.2.2.4 Sb-Te Alloys	177
	8.3 Short-Range Order	179
	8.3.1 X-ray Absorption	179
	8.3.1.1 Short-range Order in Crystalline GeTe	183
	8.3.1.2 Short-range Order in Amorphous GeTe	184
	8.3.1.3 Short-range Order in Crystalline Ge2Sb2Te5	186
	8.3.2 Short Range Order in Sb-Te Alloys	189
	8.3.2.1 Conclusions	190
	References	190
	9. Optical and Electrical Properties of Phase Change Materials	194
	9.1 Introduction	194
	9.2 Optical Constants and Optical Bandgap	195
	9.2.1 Determination of the Optical Constants and Absorption Coefficient	195
	9.2.1.1 Transmission and Reflection Measurements	196
	9.2.1.2 Ellipsometry	196
	9.2.1.3 Optical Contrast between Amorphous and Crystalline Phases	197
	9.2.2 Optical Bandgap	198
	9.2.3 Infrared Absorption: Band Tails and Free Carrier Absorption	200
	9.2.3.1 Urbach Edge	200
	9.2.3.2 Free Carrier Absorption	201
	9.2.4 Effects of Composition and Preparation Conditions	201
	9.3 Photo-induced Effects	203
	9.3.1 Photo-induced Current and Optical Nonlinearity	203
	9.3.2 Photo-Oxidation	204
	9.4 Conductivity and Phase Transformation	205
	9.4.1 Temperature-dependence of Resistivity	205
	9.4.2 Intermediate States: Percolation and Multilevel Recording	206
	9.4.3 Effects of Composition and Processing Conditions	207
	9.5 Electronic Transport Properties and Band Structure	208
	9.5.1 Characterization of Transport Properties	208
	9.5.1.1 Hall Measurements	208
	9.5.1.2 Thermoelectric Effect	209
	9.5.2 Hexagonal Ge2Sb2Te5	210
	9.5.3 Face-centered-cubic Ge2Sb2Te5	212
	9.5.4 Amorphous Ge2Sb2Te5	213
	9.6 Perspective for the Future	213
	References	214
	10. Development of Materials for Third Generation Optical Storage Media	218
	10.1 Introduction	218
	10.2 Requirements for a Phase-change Material	219
	10.3 Why Chalcogenide Semiconductors for Optical Memory?	221
	10.4 Merits and Demerits of the Te Based Eutectic Alloys	222
	10.5 Merits and Demerits of the Te-based Single Phase Materials	225
	10.6 From Eutectic to Single Phase Compositions	227
	10.7 Discovery of the GeTe-Sb2Te3 Pseudo-binary System	228
	10.8 Importance of the Cubic Structure and Vacancies	232
	10.9 Secrets of the Present Phase-change Materials I	234
	10.10 Materials for Blue Laser and Multi-layer Applications	238
	10.11 Secrets of Present Phase-change Materials II	241
	10.12 Conclusions	242
	References	243
	11. Novel Deposition Methods	246
	11.1 Chemical Vapor Phase Deposition	246
	11.2 Electrodeposition	252
	11.3 Solution-phase Deposition	257
	11.4 Nanomaterials	260
	11.5 Conclusions	262
	References	263
	Part II: Applications: Optical, Solid State Memory and Reconfigurable Logic	268
	12. Optical Memory: From 1st to 3rd Generation and its Future	269
	12.1 Introduction	269
	12.2 Three Generations of Optical Media	270
	12.2.1 The First Generation: Compact Discs (CDs)	271
	12.2.2 The Second Generation: Digital Versatile Disks (DVDs)	271
	12.2.3 The Third Generation: Blu-ray Discs (BDs)	274
	12.2.3.1 Blu-ray Discs	274
	12.3 The Basic Principle of Optical Recording	275
	12.4 Phase-change Optical Recording and Related Technologies	278
	12.4.1 Phase-Change Optical Storage	278
	12.4.1.1 Principle of Phase-Change Optical Storage	278
	12.4.1.2 Phase-Change Materials	281
	12.4.1.3 Development of Phase-Change Optical Storage Media	282
	12.4.1.4 Disc Structure of Phase-Change Optical Disc	285
	12.4.1.5 Models of Phase-Change Induced by Moving Laser Beam	287
	12.4.2 Techniques for Phase-Change Optical Storage	288
	12.4.2.1 Short Wavelength Laser Diodes	289
	12.4.2.2 Large Numerical Aperture (NA)	289
	12.4.2.3 Land/Groove Recording	289
	12.4.2.4 Write Strategy	290
	12.4.2.5 Cross Talk	291
	12.4.2.6 Super Resolution	292
	12.4.2.7 Multilevel Phase-Change Recording	293
	12.4.2.8 Dual Layer Phase-change Optical Recording	293
	12.4.2.9 Superlattice-like Phase-change Optical Disc	294
	12.4.2.10 Initialization Free Phase-change Optical Disc	295
	12.4.2.11 Near-field Phase-Change Optical Storage	297
	12.5 The Future of Optical Storage	297
	References	300
	13. 4th Generation Optical Memories Based on Super-resolution Near-field structure (Super-RENS) and Near-field Optics	303
	13.1 Introduction	303
	13.2 Diffraction Limit and Near-Field Optics	304
	13.3 Small Aperture and Non-propagating Photons	306
	13.4 Super-resolution Near-field Structure (Super-RENS) Principle to Retrieve Non-propagating Light	308
	13.5 Origin of the Strong Scattered Signals for 4th Generation Super-RENS Disks	310
	13.6 Beyond Super-RENS	314
	References	315
	14. Phase Change Memory Device Modeling	317
	14.1 Introduction	317
	14.2 Device Operation	318
	14.3 Modeling of Electrical Conduction in the Amorphous Phase	320
	14.4 Threshold Switching in the Amorphous Chalcogenide	324
	14.5 Modeling the Electrical Conduction in the Crystalline Chalcogenide	326
	14.6 Electro-thermal Modeling of the Programming Characteristics	327
	14.7 Modeling the Amorphous to Crystalline Phase Transformation	332
	14.8 Modeling the Structural Relaxation in the Amorphous Phase	338
	14.9 Summary and Outlook	343
	References	345
	15. Phase Change Random Access Memory Advanced Prototype Devices and Scaling	348
	15.1 Introduction	348
	15.2 Device Scaling by Reducing the Electrode Contact Area	349
	15.2.1 The Heater Structure	350
	15.2.1.1 Additional Adhesion Layer	351
	15.2.1.2 Size Effect of the Phase Change Material	352
	15.2.1.3 Different Phase Change Materials	353
	15.2.1.4 Process Integration Issues for Scaling	353
	15.2.2 The Edge Contact Structure	354
	15.2.3 ?Trench Structure	355
	15.2.4 The Ring Structure	355
	15.3 Device Scaling by Reducing the Phase Change Material Volume	356
	15.3.1 The Pillar Structure	357
	15.3.2 The Line Structure	358
	15.3.3 The Bridge Structure	359
	15.4 Other Prototype Devices	360
	15.4.1 Scaling Both the Material and the Contact	361
	15.4.2 Multi-level Cell	362
	15.4.3 Confined Structure	362
	15.5 Advanced Device Testing	364
	15.6 Summary	366
	References	367
	16. Phase Change Memory Cell Concepts and Designs	372
	16.1 Introduction	372
	16.2 Technology Overview	373
	16.3 Phase Change Memory Cell Electrical Characterization	378
	16.4 Phase Change Memory Cell Reliability	385
	16.4.1 Data Retention Characterization	386
	16.4.2 Retention Behavior with Device Scaling	393
	16.4.3 Cycling Endurance	394
	16. 5 Summary and Outlook	395
	References	396
	17. Phase Change Random Access Memory Integration	398
	17.1 Introduction	398
	17.2 Phase Change Random Access Memory Design Basics	399
	17.3 Review of Desired Phase Change Memory CellCharacteristics	403
	17.4 The Access Device	407
	17.5 Device Design Considerations	410
	17.5.1 The Mushroom Cell without or with Bottom RingElectrode	410
	17.5.2 The Pillar Cell	414
	17.5.3 The ?Trench Cell	416
	17.5.4 The Pore Cell	416
	17.6 Multi-Level Phase Change Random Access Memory	420
	17.7 Concluding Remarks	423
	References	423
	18. Reconfigurable Logic	426
	18.1 Introduction	426
	18.2 Digital System Basics	427
	18.3 Simple Configurable Digital Systems	431
	18.4 Considerations in Computation Architectures	436
	18. 5 Multi-valued Systems	437
	18.6 Threshold Logic	439
	18.7 Artificial Neural Networks	442
	18.8 Other Analog-domain Programmable Systems	443
	18.9 Conclusions	446
	References	446
	Author Bios	448
	Index	454