Contents
List of contributors xi
1 The ubiquitous nature of chalcogenides in science and technology 1
J.K. Furdyna, S.-N. Dong, S. Lee, X. Liu and M. Dobrowolska
1.1 Introduction 1
1.2 Chalcogenides in 3D form 2
1.2.1 Monocrystalline CdTe solar cells 2
1.2.2 II-VI magnetic semiconductors 3
1.2.3 Electronic and optical effects in II1-xMnxVI alloys 4
1.2.4 Miscellaneous II-VI-based diluted magnetic semiconductors 5
1.2.5 Chalcogenide lead salts 7
1.2.6 Chalcogenide spinels 9
1.3 Two-dimensional chalcogenide structures 9
1.3.1 Epitaxially-formed chalcogenides 9
1.3.2 2D “van der Waals” chalcogenides 12
1.3.3 Interface phenomena in chalcogenide structures 15
1.4 Chalcogenides beyond 2D 19
1.4.1 One-dimensional and quasi-one-dimensional chalcogenides 19
1.4.2 Zero-dimensional chalcogenide structures 20
1.5 Concluding remarks 22
References 23
2 Thermoelectric applications of chalcogenides 31
Han Meng, Meng An, Tengfei Luo and Nuo Yang
2.1 Introduction 31
2.1.1 Thermoelectric effect 32
2.1.2 Thermoelectric efficiency 32
2.2 Nanostructure engineering 34
2.2.1 Bottom-up and top-down fabrication 34
2.2.2 Consolidation method 35
2.2.3 Introducing nanostructures 36
2.2.4 Introducing nanoprecipitates 37
2.3 Defect engineering 38
2.3.1 Normal doping 38
2.3.2 Introducing point defect 40
2.3.3 Introducing element deficiency 40
2.3.4 Other approaches 41
2.4 Band structure engineering 43
2.5 Crystal structure engineering 44
2.5.1 Original complex structure 44
2.5.2 Peierls distortion structure 45
2.5.3 Layered structure 46
2.5.4 Increase the degree of orientation 48
2.6 Outlook 49
References 51
3 Lead salt photodetectors and their optoelectronic characterization 57
D. Babic, L.W. Johnson, L.V. Snyder and J.J. San Roman
3.1 Introduction 57
3.2 Background 57
3.3 Lead salt detector fabrication 59
3.4 Lead salt detector characterization 60
3.5 Conclusions 64
Acknowledgment 64
References 64
4 Optical dispersion of ternary II_VI semiconductor alloys 67
Xinyu Liu and J.K. Furdyna
4.1 Introduction 67
4.1.1 The classical picture of dispersion 67
4.1.2 Electronic band structure and dispersion 69
4.1.3 The phenomenological dispersion model 71
4.2 Optical dispersion 72
4.2.1 Determination of the energy gap Eg(x) 73
4.2.2 Indices of refraction n(x) 76
4.3 Theoretical model 83
4.3.1 Semi-empirical model 83
4.3.2 Improvements of SEO model 85
4.3.3 Comparison between various semi-empirical fits for ZnTe 88
4.4 Data analysis and discussion 91
4.4.1 Experimental results for ternary II-VI alloys 91
4.4.2 Summary 95
4.5 Physical interpretation and discussion 99
4.5.1 Physical meaning of fitting parameters 99
4.5.2 Optical dispersion and ionicity 105
References 107
Appendix 109
5 Group-IV monochalcogenides GeS, GeSe, SnS, SnSe 119
Lyubov V. Titova, Benjamin M. Fregoso and Ronald L. Grimm
5.1 Introduction 119
5.2 Crystal lattice and band structure calculations 120
5.3 Electronic band structure 123
5.4 Electronic and optical properties 126
5.5 Nonlinear optical properties 131
5.6 Fabrication: single crystal growth and exfoliation; CVD, growth
of 2D nanostructures 137
Acknowledgment 140
References 140
Further reading 150
6 Epitaxial II-VI semiconductor quantum structures involving dilute
magnetic semiconductors 153
S. Lee, M. Dobrowolska and J.K. Furdyna
6.1 Introduction 153
6.2 Magneto-optical properties of ZnSe and ZnTe epilayers 155
6.2.1 Band structure and exciton 155
6.2.2 Exciton transitions in the absence of magnetic field 157
6.3 Landau level transitions and magneto-polaron effect 158
6.4 Composition modulated ZnSeTe sinusoidal superlattice 161
6.4.1 Band structure of superlattice with sinusoidal energy profile 162
6.4.2 Growth of ZnSeTe superlattices with sinusoidal composition
modulation 163
6.4.3 Optical transitions in ZnSeTe sinusoidal superlattices 165
6.5 II-VI-based zero-dimensional structures 166
6.5.1 Spin polarization and relaxation of exciton in QDs 167
6.5.2 Spin-spin interaction between the coupled QDs 171
6.6 II-VI quantum structures involving DMSs 173
6.6.1 Zeeman splitting in II1-xMnxVI DMS epilayers 173
6.6.2 Mapping of exciton localization in QDs 174
6.7 Enhancement of spin polarization in non-DMS and DMS coupled
QDs 178
6.8 Summary 181
References 182
7 2D electron gas in chalcogenide multilayers 189
A. Kazakov and T. Wojtowicz
7.1 Introduction 189
7.2 2DEG in magnetically doped QWs 190
7.2.1 2DEG in low-dimensional heterostructures 190
7.2.2 Spin interactions in chalcogenide DMS QWs 193
7.2.3 Magnetotransport in chalcogenide QWs 195
7.2.4 DMS QW in inhomogeneous magnetic fields 206
7.2.5 DMS QWs under terahertz and microwave radiation 209
7.3 Novel topological phases in chalcogenide multilayers 211
7.3.1 Domain walls and non-Abelian excitations 212
7.3.2 Wireless Majorana bound states 217
7.3.3 Quantum spin Hall effect in HgTe QWs 217
7.3.4 Quantum anomalous Hall effect in HgTe QWs 219
7.3.5 Topological phases in IV-VI materials 220
7.4 Summary and perspectives 220
Acknowledgment 221
References 221
8 Layered two-dimensional selenides and tellurides grown
by molecular beam epitaxy 235
Xinyu Liu, J.K. Furdyna, Sergei Rouvimov, Suresh Vishwanath,
Debdeep Jena, Huili Grace Xing and David J. Smith
8.1 Introduction 235
8.1.1 Motivation 235
8.1.2 A survey of 2D chalcogenides 237
8.2 MBE growth of 2D materials 237
8.2.1 Advantages of MBE growth of 2D materials 237
8.2.2 Growth of layered selenide and telluride films and their heterostructures 242
8.2.3 Cross between 2D and 3D structures 249
8.2.4 Challenges 252
8.3 Physical characterization of 2D materials grown by MBE 253
8.3.1 Electronic structure of 2D materials 253
8.3.2 Phonon properties of 2D materials 255
8.3.3 Other optical properties of 2d materials 257
8.4 Concluding remarks 261
Acknowledgment 262
References 262
9 Tailoring exchange interactions in magnetically doped II-VI nanocrystals 271
Rachel Fainblat, Franziska Muckel and Gerd Bacher
9.1 Introduction 271
9.1.1 Theoretical background 272
9.1.2 Outline of the chapter 275
9.2 Two-dimensional (2D) colloidal nanocrystals 275
9.2.1 Giant magneto-optical response in Mn21-doped CdSe nanoribbons 275
9.2.2 Tuning magnetic exchange interactions by wavefunction engineering in core/shell nanoplatelets 279
9.3 Zero-dimensional nanocrystals 282
9.3.1 Valence-band mixing in doped nanocrystal quantum dots 282
9.3.2 Going to the limit: individual dopants in single nanocrystals quantum dots 285
9.4 At the border between quantum dots and molecules: magic sized nanoclusters 289
9.4.1 Smallest doped semiconductors 289
9.4.2 Doped magic-sized alloy nanoclusters 290
9.4.3 “Digital” doping in nanoclusters 292
9.5 Conclusion and future trends 294
Acknowledgments 295
References 296
10 Chalcogenide topological insulators 305
Joseph A. Hagmann
10.1 Introduction 305
10.1.1 The Z2 Topological insulator 306
10.1.2 Mercury telluride quantum wells 307
10.1.3 V2VI3-series 3D topological insulators 309
10.2 Synthesis 312
10.2.1 Mercury telluride quantum well growth 312
10.2.2 V2VI3-series 3D topological insulators 314
10.3 Experimental investigations 318
10.3.1 Spectroscopy 318
10.3.2 Electrical transport 321
10.3.3 Exotic topological states 323
10.4 Summary and outlook 327
References 329
Further reading 336
11 Thermal transport of chalcogenides 339
Meng An, Han Meng, Tengfei Luo and Nuo Yang
11.1 Introduction 339
11.1.1 Basic theory of heat conduction 339
11.1.2 The structure characteristics of chalcogenides 342
11.2 Geometrical effect 343
11.2.1 Dimensional effect 343
11.2.2 Length dependence 346
11.2.3 Single-layer sheet 348
11.2.4 Discussion on the overall trend from single-layer to bulk 351
11.3 Extrinsic thermal conductivity of chalcogenide 352
11.3.1 Strain effect 352
11.3.2 Effect of atomic disorder and defect 355
11.3.3 Anisotropy 358
11.4 Fundamental insight into thermal transport 360
11.4.1 Resonant bonding 360
11.4.2 Lone pair electron 361
11.4.3 Rattling modes 363
11.5 Conclusion and outlook 364
References 364
Index 371