Quantum Materials, Lateral Semiconductor Nanostructures, Hybrid Systems and Nanocrystals (eBook)

Lateral Semiconductor Nanostructures, Hybrid Systems and Nanocrystals

Detlef Heitmann (Herausgeber)

eBook Download: PDF

2010
XX, 434 Seiten
Springer Berlin (Verlag)
9783642105531 (ISBN)

Infos

Semiconductor nanostructures are ideal systems to tailor the physical properties via quantum effects, utilizing special growth techniques, self-assembling, wet chemical processes or lithographic tools in combination with tuneable external electric and magnetic fields. Such systems are called 'Quantum Materials'.The electronic, photonic, and phononic properties of these systems are governed by size quantization and discrete energy levels. The charging is controlled by the Coulomb blockade. The spin can be manipulated by the geometrical structure, external gates and by integrating hybrid ferromagnetic emitters.This book reviews sophisticated preparation methods for quantum materials based on III-V and II-VI semiconductors and a wide variety of experimental techniques for the investigation of these interesting systems. It highlights selected experiments and theoretical concepts and gives such a state-of-the-art overview about the wide field of physics and chemistry that can be studied in these systems.

Detlef Heitmann is a Full Professor at the Institute of Applied Physics of the University of Hamburg and Head of the Semiconductor Group. After research on Cerenkov radiation, surface plasmons and Integrated Optics he entered the field of low-dimensional semiconductor systems. His interest was devoted in particular to the fabrication of quantum structures and its investigation with far infrared, Raman and photoluminescence spectroscopy. In recent years his group also used the tools of the semiconductor technology to prepare ferromagnetic nanostructures and study the spin dynamics in these systems, and to fabricate and investigate optical metamaterials. From 1997 to 2009 he was Speaker of the DFG Collaborative Research Center SFB 508 'Quantum Materials'.

Inhalt

Preface 6
Contents 10
Contributors 18
1 Self-Assembly of Quantum Dots and Rings on Semiconductor Surfaces 22
1.1 Introduction 22
1.1.1 Molecular Beam Epitaxy 24
1.1.2 Kinetics of Crystal Growth 25
1.2 Strain-Driven InAs QDs in Stranski–Krastanov Mode 27
1.3 Droplet Epitaxy in Volmer–Weber Mode 32
1.4 Local Droplet Etching 35
1.4.1 Structural Properties of LDE Nanoholes and Rings 36
1.4.2 Fabrication of QDs by Filling of LDE Nanoholes 40
1.5 Conclusions 42
References 43
2 Curved Two-Dimensional Electron Systemsin Semiconductor Nanoscrolls 46
2.1 Introduction 46
2.2 The Basic Principle Behind ``Rolled-Up Nanotech'' 49
2.3 First Evidence of Rolled-up 2DES in FreestandingCurved Lamellae 54
2.4 2DES in Rolled-Up Hall Bars: Static SkinEffect, Magnetic Barriers, and Reflected Edge Channels 60
2.4.1 Low Magnetic Field Regime: Static SkinEffect and Magnetic Barriers 61
2.4.2 High Magnetic Field Regime: Reflected Edge Channels 63
2.5 Conclusions 67
References 68
3 Capacitance Spectroscopy on Self-Assembled Quantum Dots 71
3.1 Introduction 71
3.2 Experimental Techniques 72
3.2.1 Deep Level Transient Spectroscopy 72
3.2.2 Capacitance Voltage Spectroscopy on Schottky Diodes 76
3.3 Experimental Results 77
3.3.1 Capacitance Spectroscopy on Quantum-DotSchottky Diodes 77
3.3.2 Deep Level Transient Spectroscopy on Quantum-Dot Schottky Diodes 79
3.3.3 Evaluation of Quantum-Dot Shell Energies in the Thermally Assisted Tunneling Model 82
3.3.4 DLTS Experiments in Magnetic Fields 87
3.3.5 Advanced Time-Resolved CapacitanceSpectroscopy Methods: Tunneling-DLTS,Constant-Capacitance DLTS and Reverse-DLTS 89
3.3.6 Alternative Capacitance Spectroscopy Methods 92
3.4 Conclusion and Outlook 93
References 95
4 The Different Faces of Coulomb Interaction in Transport Through Quantum Dot Systems 98
4.1 Introduction 98
4.2 Transport Through Quantum Dot Systems 99
4.3 Electronic Structure of Quantum Dots 102
4.3.1 Circular Quantum Dots 102
4.3.2 Elliptical Quantum Dots 104
4.3.3 Quantum Rings 106
4.3.4 Magnetically Doped Quantum Dots 108
4.3.5 Correlations Beyond Hund's Rule 112
4.4 Transport Beyond Spectroscopy 114
4.5 Outlook 116
References 118
5 Far-Infrared Spectroscopy of Low-Dimensional Electron Systems 121
5.1 Introduction 121
5.2 Experimental FIR Spectroscopic Techniques 122
5.3 Preparation of Arrays of Quantum Materials 124
5.4 Theoretical Models 126
5.5 Far-infrared Transmission Experiments 130
5.6 FIR Photoconductivity Spectroscopy 137
5.7 Summary 153
References 154
6 Electronic Raman Spectroscopy of Quantum Dots 157
6.1 Introduction 157
6.2 Fabrication of Charged Quantum Dots 159
6.3 Electronic States in Quantum Dots 160
6.4 Raman Experiments on Etched GaAs–AlGaAs QDs 163
6.4.1 QDs with Many Electrons 163
6.4.2 QDs with Only Few Electrons 167
6.5 Raman Experiments on Self-Assembled In(Ga)As QDs 168
6.5.1 QDs with a Fixed Number of Electrons, Ne 6–7 168
6.5.2 QDs with a Tunable Number of Electrons, Ne=2 …6 169
6.5.3 Comparison to Calculated Resonant Raman Spectra for Ne=2 …6 172
6.5.4 QDs with Ne=2 Electrons: Artificial He Atoms 174
6.6 Summary 178
References 180
7 Light Confinement in Microtubes 182
7.1 Introduction 182
7.2 Fabrication 184
7.3 Experimental Setup 185
7.4 Microtubes with Unstructured Rolling Edges 185
7.5 Influence of the Rolling Edges on the Emission Properties 188
7.6 Controlled Three-Dimensional Confinement by Structured Rolling Edges 190
7.7 Conclusion and Outlook 197
References 198
8 Scanning Tunneling Spectroscopy of Semiconductor Quantum Dots and Nanocrystals 200
8.1 Introduction 200
8.2 Electronic Structure and Single-Particle Wavefunctions 201
8.3 Electron Transport Through Quantum Dots and Nanocrystals 204
8.3.1 Tunneling Spectroscopy 204
8.3.2 Coulomb Blockade 207
8.3.3 Shell-Tunneling and Shell-Filling Spectroscopy 208
8.4 MBE-Grown Quantum Dots 211
8.4.1 Scanning Tunneling Microscopyand Cross-Sectional STM 211
8.4.2 Wavefunction Mapping of MBE-GrownInAs Quantum Dots 214
8.4.3 Coulomb Interactions and Correlation Effects 218
8.5 Colloidal Nanocrystals 222
8.5.1 Electronic Properties, Atomic-Like States, and Charging Multiplets 222
8.5.2 Electronic Wavefunctions in Immobilized Semiconductor Nanocrystals 225
8.6 Conclusions 228
References 229
9 Scanning Tunneling Spectroscopy on III–V Materials: Effects of Dimensionality, Magnetic Field, and Magnetic Impurities 234
9.1 Introduction 234
9.2 Interpreting STM and STS Data 235
9.2.1 Assumptions 238
9.2.2 Tip-Induced Band Bending 238
9.2.3 Experimental Procedures 241
9.3 Electrons in Different Dimensions 241
9.3.1 Overview 241
9.3.2 Three-Dimensional Electron System (3DES) 242
9.3.3 Comparison of 2DES and 3DES 245
9.3.4 2DES in a Magnetic Field 247
9.4 Magnetic Acceptors 251
9.4.1 Overview 251
9.4.2 Determining the Depth Below the (110) Surface 252
9.4.3 Acceptor Charge Switching by Tip-Induced Band Bending 253
9.4.4 Properties of the Hole Bound to the Mn Acceptor 255
9.5 Conclusions and Outlook 256
References 257
10 Magnetization of Interacting Electrons in Low-Dimensional Systems 261
10.1 Introduction 261
10.2 Highly Sensitive Magnetometry 262
10.2.1 Figures-of-Merit 262
10.2.2 SQUID Magnetometer 264
10.2.3 Concepts of Torque Magnetometry 265
10.2.4 Torsion-Balance Magnetometers 266
10.2.5 Cantilever Magnetometers 267
10.3 Theory of Magnetic Quantum Oscillations 271
10.3.1 Thermodynamics Definition of Magnetization 272
10.3.2 DHvA Effect in 2DESs 272
10.4 Experimental Results on 2DESs 273
10.4.1 DOS and Energy Gaps at Even Integer 274
10.4.2 Energy Gaps at Odd Integer 277
10.4.3 Fractional QHE Gaps 278
10.5 Magnetization of Nanostructures 279
10.5.1 Magnetization of AlGaAs/GaAs Quantum Wires 279
10.5.2 Magnetization of AlGaAs/GaAs Quantum Dots 283
10.6 Conclusions 288
References 289
11 Spin Polarized Transport and Spin Relaxation in Quantum Wires 292
11.1 Introduction 292
11.2 Spin-Dynamics in Semiconductor Quantum Wires 293
11.2.1 Spin-Orbit Interaction in Semiconductors 293
11.2.2 Spin Diffusion 297
11.2.3 Spin Relaxation Mechanisms 299
11.2.4 Spin Dynamics in Quantum Wires 301
11.2.4.1 Comparison with Experiments 305
11.3 Spin Polarized Currents in Quantum Wires 307
11.3.1 Self-Duality and Spin Polarization 307
11.3.2 Spin Filtering Effect by Nonuniform Rashba SOC 308
11.3.3 Generation of the Spin-Polarized Current in a T-Shape Conductor 310
11.4 Critical Discussion and Future Perspective 314
References 315
12 InAs Spin Filters Based on the Spin-Hall Effect 318
12.1 Introduction 318
12.2 Spin–Orbit Coupling 319
12.2.1 Spin–Orbit Coupling in Vacuum 319
12.2.2 Spin–Orbit Coupling in III–V Semiconductors 320
12.3 Spin Hall Effect 322
12.3.1 Extrinsic Spin Hall Effect 323
12.3.2 Intrinsic Spin Hall Effect 324
12.3.3 Experimental Detection of the Spin Hall Effect 324
12.4 Spin Filters 325
12.5 Device Layout 326
12.6 Experiments 331
12.6.1 Characterization of Single Quantum Point Contacts 331
12.6.2 Characterization of Spin-Filter Cascades 332
12.6.3 Quantized Conductance 335
12.6.4 Correlation Between Conductance Channels and Conductance Portions 337
12.7 Summary 337
12.7.1 Conclusions 337
12.7.2 Outlook 339
References 340
13 Spin Injection and Detection in Spin Valves with Integrated Tunnel Barriers 342
13.1 Introduction 342
13.2 First Experiments 343
13.3 Spin Injection and Detection in Spin Valves 344
13.3.1 Theory 344
13.3.2 Permalloy Electrodes for Spin-Valve Devices 350
13.3.2.1 Magnetic Characterization of Permalloy Electrodes 351
13.3.2.2 Dependence of Specific Resistance on Substrate Temperature 353
13.3.2.3 Dependence of Spin Polarization on Layer Thickness 354
13.3.3 Spin Valves with Insulating Barriers 356
13.3.4 Connecting Paramagnetic Channel 359
13.4 Outlook 364
References 365
14 Growth and Characterization of Ferromagnetic Alloys for Spin Injection 367
14.1 Introduction 367
14.2 Experimental 372
14.2.1 Growth and Structure Investigations 372
14.2.2 Electrical Characterization 373
14.3 Results and Discussions 376
14.3.1 Thin Films 376
14.3.2 Nanopatterning 381
14.3.3 Heusler-Based Spin-Valves 382
14.4 Conclusions 384
References 385
15 Charge and Spin Noise in Magnetic Tunnel Junctions 387
15.1 Introduction 388
15.2 Noise and Magnetization Dynamics 389
15.3 Langevin-Approach 392
15.4 Fokker–Planck Approach to Spin-Torque Switching 398
15.5 Switching Time of Spin-Torque Structures 404
15.6 Conclusions 406
References 407
16 Nanostructured Ferromagnetic Systems for the Fabrication of Short-Period Magnetic Superlattices 409
16.1 Introduction 409
16.2 Multilayer Films with Perpendicular Anisotropy 411
16.3 Nanostructuring 416
16.3.1 Fabrication of Diblock Copolymer Micelles Filled with SiO2 416
16.3.2 Monomicellar Layers on Substrates 416
16.3.3 Fabrication of Antidot Arrays UtilizingMonomicellar Layers 417
16.3.4 Fabrication of Dot Arrays Utilizing Monomicellar Layers 419
16.4 Magnetic Behavior of Multilayers and Nanostructures 422
16.4.1 Multilayers 422
16.4.2 Dots 425
16.5 Summary 426
References 427
17 How X-Ray Methods Probe Chemically Prepared Nanoparticles from the Atomic- to the Nano-Scale 430
17.1 Local Atomic Structure: Chemical Stateand Coordination 430
17.2 Crystallinity and Cluster Structure 434
17.3 Core–Shell Structures on the Nanoscale 436
17.4 Summary 439
References 440
Index 441

Produkt-Details

• Erscheint lt. Verlag: 20.8.2010
• Reihe/Serie: NanoScience and Technology
• Reihe/Serie: NanoScience and Technology
• Zusatzinfo: XX, 434 p. 170 illus., 30 illus. in color.
• Verlagsort: Berlin
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Chemie
• Themenwelt: Naturwissenschaften ► Physik / Astronomie
• Themenwelt: Technik ► Maschinenbau
• Schlagworte: Chemistry • Cluster • Hybrid Systems • Lithographic tools • Nanogrowth techniques • nanostructure • Quantum effects • Quantum materials • Self-assembling of nanostructures • semiconductor • Semiconductor Nanocrystals • Semiconductor Nanostructures • spectroscopy • superlattices • Surface • Surfaces • Transport
• ISBN-13: 9783642105531 / 9783642105531