Heitmann Quantum Materials, Lateral Semiconductor Nanostructures, Hybrid Systems and Nanocrystals

Lateral Semiconductor Nanostructures, Hybrid Systems and Nanocrystals
1. Auflage 2010
ISBN: 978-3-642-10553-1
Verlag: Springer
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 434 Seiten

Reihe: NanoScience and Technology

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'.

Autoren/Hrsg.

Heitmann, Detlef

Inhaltsverzeichnis

1;Preface;6
2;Contents;10
3;Contributors;18
4;1 Self-Assembly of Quantum Dots and Rings on Semiconductor Surfaces;22
4.1;1.1 Introduction;22
4.1.1;1.1.1 Molecular Beam Epitaxy;24
4.1.2;1.1.2 Kinetics of Crystal Growth;25
4.2;1.2 Strain-Driven InAs QDs in Stranski–Krastanov Mode;27
4.3;1.3 Droplet Epitaxy in Volmer–Weber Mode;32
4.4;1.4 Local Droplet Etching;35
4.4.1;1.4.1 Structural Properties of LDE Nanoholes and Rings;36
4.4.2;1.4.2 Fabrication of QDs by Filling of LDE Nanoholes;40
4.5;1.5 Conclusions;42
4.6;References;43
5;2 Curved Two-Dimensional Electron Systemsin Semiconductor Nanoscrolls;46
5.1;2.1 Introduction;46
5.2;2.2 The Basic Principle Behind ``Rolled-Up Nanotech'';49
5.3;2.3 First Evidence of Rolled-up 2DES in FreestandingCurved Lamellae;54
5.4;2.4 2DES in Rolled-Up Hall Bars: Static SkinEffect, Magnetic Barriers, and Reflected Edge Channels;60
5.4.1;2.4.1 Low Magnetic Field Regime: Static SkinEffect and Magnetic Barriers;61
5.4.2;2.4.2 High Magnetic Field Regime: Reflected Edge Channels;63
5.5;2.5 Conclusions;67
5.6;References;68
6;3 Capacitance Spectroscopy on Self-Assembled Quantum Dots;71
6.1;3.1 Introduction;71
6.2;3.2 Experimental Techniques;72
6.2.1;3.2.1 Deep Level Transient Spectroscopy;72
6.2.2;3.2.2 Capacitance Voltage Spectroscopy on Schottky Diodes;76
6.3;3.3 Experimental Results;77
6.3.1;3.3.1 Capacitance Spectroscopy on Quantum-DotSchottky Diodes;77
6.3.2;3.3.2 Deep Level Transient Spectroscopy on Quantum-Dot Schottky Diodes;79
6.3.3;3.3.3 Evaluation of Quantum-Dot Shell Energies in the Thermally Assisted Tunneling Model;82
6.3.4;3.3.4 DLTS Experiments in Magnetic Fields;87
6.3.5;3.3.5 Advanced Time-Resolved CapacitanceSpectroscopy Methods: Tunneling-DLTS,Constant-Capacitance DLTS and Reverse-DLTS;89
6.3.6;3.3.6 Alternative Capacitance Spectroscopy Methods;92
6.4;3.4 Conclusion and Outlook;93
6.5;References;95
7;4 The Different Faces of Coulomb Interaction in Transport Through Quantum Dot Systems;98
7.1;4.1 Introduction;98
7.2;4.2 Transport Through Quantum Dot Systems;99
7.3;4.3 Electronic Structure of Quantum Dots;102
7.3.1;4.3.1 Circular Quantum Dots;102
7.3.2;4.3.2 Elliptical Quantum Dots;104
7.3.3;4.3.3 Quantum Rings;106
7.3.4;4.3.4 Magnetically Doped Quantum Dots;108
7.3.5;4.3.5 Correlations Beyond Hund's Rule;112
7.4;4.4 Transport Beyond Spectroscopy;114
7.5;4.5 Outlook;116
7.6;References;118
8;5 Far-Infrared Spectroscopy of Low-Dimensional Electron Systems;121
8.1;5.1 Introduction;121
8.2;5.2 Experimental FIR Spectroscopic Techniques;122
8.3;5.3 Preparation of Arrays of Quantum Materials;124
8.4;5.4 Theoretical Models;126
8.5;5.5 Far-infrared Transmission Experiments;130
8.6;5.6 FIR Photoconductivity Spectroscopy;137
8.7;5.7 Summary;153
8.8;References;154
9;6 Electronic Raman Spectroscopy of Quantum Dots;157
9.1;6.1 Introduction;157
9.2;6.2 Fabrication of Charged Quantum Dots;159
9.3;6.3 Electronic States in Quantum Dots;160
9.4;6.4 Raman Experiments on Etched GaAs–AlGaAs QDs;163
9.4.1;6.4.1 QDs with Many Electrons;163
9.4.2;6.4.2 QDs with Only Few Electrons;167
9.5;6.5 Raman Experiments on Self-Assembled In(Ga)As QDs;168
9.5.1;6.5.1 QDs with a Fixed Number of Electrons, Ne 6–7;168
9.5.2;6.5.2 QDs with a Tunable Number of Electrons, Ne=2 …6;169
9.5.3;6.5.3 Comparison to Calculated Resonant Raman Spectra for Ne=2 …6;172
9.5.4;6.5.4 QDs with Ne=2 Electrons: Artificial He Atoms;174
9.6;6.6 Summary;178
9.7;References;180
10;7 Light Confinement in Microtubes;182
10.1;7.1 Introduction;182
10.2;7.2 Fabrication;184
10.3;7.3 Experimental Setup;185
10.4;7.4 Microtubes with Unstructured Rolling Edges;185
10.5;7.5 Influence of the Rolling Edges on the Emission Properties;188
10.6;7.6 Controlled Three-Dimensional Confinement by Structured Rolling Edges;190
10.7;7.7 Conclusion and Outlook;197
10.8;References;198
11;8 Scanning Tunneling Spectroscopy of Semiconductor Quantum Dots and Nanocrystals;200
11.1;8.1 Introduction;200
11.2;8.2 Electronic Structure and Single-Particle Wavefunctions;201
11.3;8.3 Electron Transport Through Quantum Dots and Nanocrystals;204
11.3.1;8.3.1 Tunneling Spectroscopy;204
11.3.2;8.3.2 Coulomb Blockade;207
11.3.3;8.3.3 Shell-Tunneling and Shell-Filling Spectroscopy;208
11.4;8.4 MBE-Grown Quantum Dots;211
11.4.1;8.4.1 Scanning Tunneling Microscopyand Cross-Sectional STM;211
11.4.2;8.4.2 Wavefunction Mapping of MBE-GrownInAs Quantum Dots;214
11.4.3;8.4.3 Coulomb Interactions and Correlation Effects;218
11.5;8.5 Colloidal Nanocrystals;222
11.5.1;8.5.1 Electronic Properties, Atomic-Like States, and Charging Multiplets;222
11.5.2;8.5.2 Electronic Wavefunctions in Immobilized Semiconductor Nanocrystals;225
11.6;8.6 Conclusions;228
11.7;References;229
12;9 Scanning Tunneling Spectroscopy on III–V Materials: Effects of Dimensionality, Magnetic Field, and Magnetic Impurities;234
12.1;9.1 Introduction;234
12.2;9.2 Interpreting STM and STS Data;235
12.2.1;9.2.1 Assumptions;238
12.2.2;9.2.2 Tip-Induced Band Bending;238
12.2.3;9.2.3 Experimental Procedures;241
12.3;9.3 Electrons in Different Dimensions;241
12.3.1;9.3.1 Overview;241
12.3.2;9.3.2 Three-Dimensional Electron System (3DES);242
12.3.3;9.3.3 Comparison of 2DES and 3DES;245
12.3.4;9.3.4 2DES in a Magnetic Field;247
12.4;9.4 Magnetic Acceptors;251
12.4.1;9.4.1 Overview;251
12.4.2;9.4.2 Determining the Depth Below the (110) Surface;252
12.4.3;9.4.3 Acceptor Charge Switching by Tip-Induced Band Bending;253
12.4.4;9.4.4 Properties of the Hole Bound to the Mn Acceptor;255
12.5;9.5 Conclusions and Outlook;256
12.6;References;257
13;10 Magnetization of Interacting Electrons in Low-Dimensional Systems;261
13.1;10.1 Introduction;261
13.2;10.2 Highly Sensitive Magnetometry;262
13.2.1;10.2.1 Figures-of-Merit;262
13.2.2;10.2.2 SQUID Magnetometer;264
13.2.3;10.2.3 Concepts of Torque Magnetometry;265
13.2.4;10.2.4 Torsion-Balance Magnetometers;266
13.2.5;10.2.5 Cantilever Magnetometers;267
13.3;10.3 Theory of Magnetic Quantum Oscillations;271
13.3.1;10.3.1 Thermodynamics Definition of Magnetization;272
13.3.2;10.3.2 DHvA Effect in 2DESs;272
13.4;10.4 Experimental Results on 2DESs;273
13.4.1;10.4.1 DOS and Energy Gaps at Even Integer ;274
13.4.2;10.4.2 Energy Gaps at Odd Integer ;277
13.4.3;10.4.3 Fractional QHE Gaps;278
13.5;10.5 Magnetization of Nanostructures;279
13.5.1;10.5.1 Magnetization of AlGaAs/GaAs Quantum Wires;279
13.5.2;10.5.2 Magnetization of AlGaAs/GaAs Quantum Dots;283
13.6;10.6 Conclusions;288
13.7;References;289
14;11 Spin Polarized Transport and Spin Relaxation in Quantum Wires;292
14.1;11.1 Introduction;292
14.2;11.2 Spin-Dynamics in Semiconductor Quantum Wires;293
14.2.1;11.2.1 Spin-Orbit Interaction in Semiconductors;293
14.2.2;11.2.2 Spin Diffusion ;297
14.2.3;11.2.3 Spin Relaxation Mechanisms;299
14.2.4;11.2.4 Spin Dynamics in Quantum Wires ;301
14.2.4.1;11.2.4.1 Comparison with Experiments;305
14.3;11.3 Spin Polarized Currents in Quantum Wires;307
14.3.1;11.3.1 Self-Duality and Spin Polarization ;307
14.3.2;11.3.2 Spin Filtering Effect by Nonuniform Rashba SOC;308
14.3.3;11.3.3 Generation of the Spin-Polarized Current in a T-Shape Conductor ;310
14.4;11.4 Critical Discussion and Future Perspective;314
14.5;References;315
15;12 InAs Spin Filters Based on the Spin-Hall Effect;318
15.1;12.1 Introduction;318
15.2;12.2 Spin–Orbit Coupling;319
15.2.1;12.2.1 Spin–Orbit Coupling in Vacuum;319
15.2.2;12.2.2 Spin–Orbit Coupling in III–V Semiconductors;320
15.3;12.3 Spin Hall Effect;322
15.3.1;12.3.1 Extrinsic Spin Hall Effect;323
15.3.2;12.3.2 Intrinsic Spin Hall Effect;324
15.3.3;12.3.3 Experimental Detection of the Spin Hall Effect;324
15.4;12.4 Spin Filters;325
15.5;12.5 Device Layout;326
15.6;12.6 Experiments;331
15.6.1;12.6.1 Characterization of Single Quantum Point Contacts;331
15.6.2;12.6.2 Characterization of Spin-Filter Cascades;332
15.6.3;12.6.3 Quantized Conductance;335
15.6.4;12.6.4 Correlation Between Conductance Channels and Conductance Portions;337
15.7;12.7 Summary;337
15.7.1;12.7.1 Conclusions;337
15.7.2;12.7.2 Outlook;339
15.8;References;340
16;13 Spin Injection and Detection in Spin Valves with Integrated Tunnel Barriers;342
16.1;13.1 Introduction;342
16.2;13.2 First Experiments;343
16.3;13.3 Spin Injection and Detection in Spin Valves;344
16.3.1;13.3.1 Theory;344
16.3.2;13.3.2 Permalloy Electrodes for Spin-Valve Devices;350
16.3.2.1;13.3.2.1 Magnetic Characterization of Permalloy Electrodes;351
16.3.2.2;13.3.2.2 Dependence of Specific Resistance on Substrate Temperature;353
16.3.2.3;13.3.2.3 Dependence of Spin Polarization on Layer Thickness;354
16.3.3;13.3.3 Spin Valves with Insulating Barriers;356
16.3.4;13.3.4 Connecting Paramagnetic Channel;359
16.4;13.4 Outlook;364
16.5;References;365
17;14 Growth and Characterization of Ferromagnetic Alloys for Spin Injection;367
17.1;14.1 Introduction;367
17.2;14.2 Experimental;372
17.2.1;14.2.1 Growth and Structure Investigations;372
17.2.2;14.2.2 Electrical Characterization;373
17.3;14.3 Results and Discussions;376
17.3.1;14.3.1 Thin Films;376
17.3.2;14.3.2 Nanopatterning;381
17.3.3;14.3.3 Heusler-Based Spin-Valves;382
17.4;14.4 Conclusions;384
17.5;References;385
18;15 Charge and Spin Noise in Magnetic Tunnel Junctions;387
18.1;15.1 Introduction;388
18.2;15.2 Noise and Magnetization Dynamics;389
18.3;15.3 Langevin-Approach;392
18.4;15.4 Fokker–Planck Approach to Spin-Torque Switching;398
18.5;15.5 Switching Time of Spin-Torque Structures;404
18.6;15.6 Conclusions;406
18.7;References;407
19;16 Nanostructured Ferromagnetic Systems for the Fabrication of Short-Period Magnetic Superlattices;409
19.1;16.1 Introduction;409
19.2;16.2 Multilayer Films with Perpendicular Anisotropy;411
19.3;16.3 Nanostructuring;416
19.3.1;16.3.1 Fabrication of Diblock Copolymer Micelles Filled with SiO2;416
19.3.2;16.3.2 Monomicellar Layers on Substrates;416
19.3.3;16.3.3 Fabrication of Antidot Arrays UtilizingMonomicellar Layers;417
19.3.4;16.3.4 Fabrication of Dot Arrays Utilizing Monomicellar Layers;419
19.4;16.4 Magnetic Behavior of Multilayers and Nanostructures;422
19.4.1;16.4.1 Multilayers;422
19.4.2;16.4.2 Dots;425
19.5;16.5 Summary;426
19.6;References;427
20;17 How X-Ray Methods Probe Chemically Prepared Nanoparticles from the Atomic- to the Nano-Scale;430
20.1;17.1 Local Atomic Structure: Chemical Stateand Coordination;430
20.2;17.2 Crystallinity and Cluster Structure;434
20.3;17.3 Core–Shell Structures on the Nanoscale;436
20.4;17.4 Summary;439
20.5;References;440
21;Index;441