NanoScience and Technology

NanoScience and Technology

Series Editors:P. Avouris B. Bhushan D. Bimberg K. von Klitzing H. Sakaki R. Wiesendanger

The series NanoScience and Technology is focused on the fascinating nano-world, meso-scopic physics, analysis with atomic resolution, nano and quantum-effect devices, nano-mechanics and atomic-scale processes. All the basic aspects and technology-oriented de-velopments in this emerging discipline are covered by comprehensive and timely books.The series constitutes a survey of the relevant special topics, which are presented by lea-ding experts in the f ield. These books will appeal to researchers, engineers, and advancedstudents.

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Stergios LogothetidisEditor

Nanostructured

Materials

and Their Applications

123

With 134 Figures

Stergios LogothetidisAristotle University of Thessaloniki

Physics DepartmentThessaloniki, Greece

Series Editors:Professor Dr. Phaedon AvourisIBM Research DivisionNanometer Scale Science & TechnologyThomas J. Watson Research CenterP.O. Box 218Yorktown Heights, NY 10598, USA

Professor Dr. Bharat BhushanOhio State UniversityNanotribology Laboratoryfor Information Storageand MEMS/NEMS (NLIM)Suite 255, Ackerman Road 650Columbus, Ohio 43210, USA

Professor Dr. Dieter BimbergTU Berlin, Fakutat Mathematik/NaturwissenschaftenInstitut fur FestkorperphyiskHardenbergstr. 3610623 Berlin, Germany

Professor Dr., Dres. h.c. Klaus von KlitzingMax-Planck-Institutfur FestkorperforschungHeisenbergstr. 170569 Stuttgart, Germany

Professor Hiroyuki SakakiUniversity of TokyoInstitute of Industrial Science4-6-1 Komaba, Meguro-kuTokyo 153-8505, Japan

Professor Dr. Roland WiesendangerInstitut fur Angewandte PhysikUniversitat HamburgJungiusstr. 1120355 Hamburg, Germany

Editor

NanoScience and Technology ISSN 1434-4904

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Laboratory for Thin Films-Nanosystems and Nanometrology

2011942603

Preface

Nanotechnology is one of the continuously emerging scientific areas combiningknowledge from the fields of Physics, Chemistry, Biology, Medicine, Informaticsand Engineering. Nanostructured materials and nanosystems are fabricated and fullycharacterised by nanotechnological tools and techniques, at sizes below 100 nm.Although there are restrictions related to nanoscale size, it is the handling andprocessing of matter at this scale that leads to the development of new and novelmaterials which may have the same bulk composition but widely varying properties.The diverse applications of nanomaterials ranging from electronic and engineeringsystems and devices, to optical and magnetic components, nanodevices in medicine,cosmetic merchandise, agricultural and food products are believed to pave the wayand have a significant economical and societal impact.

This book gives an overview of nanostructures and nanomaterials applied inthe fields of energy and organic electronics (Chap. 1). It combines the knowledgeof advanced deposition and processing methods of nanomaterials, and state-of-the-art characterization techniques with special emphasis on the optical, electrical,morphological, surface and mechanical properties (mainly in Chaps. 5 and 6).Furthermore, it contains theoretical and experimental aspects for different typesof nanomaterials, such as nanoparticles, nanotubes and thin films for organicelectronics applications. Specifically it includes topics on carbon nanomaterials andnanotubes focusing on their different synthesis routes (as shown in Chaps. 2 and 3),and full characterisation of their properties at a theoretical and experimental levelfor optoelectronics applications (as shown in Chaps. 7–9). The different depositiontechniques used to fabricate nanostructured thin films and the processing methodssuch as self-assembly and nanopatterning of surfaces are extensively described inChaps. 4 and 10.

Thessaloniki Stergios LogothetidisJuly 2011

v

Contents

1 Nanotechnology: Principles and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . 1S. Logothetidis1.1 Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Methods and Principles of Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2.1 What Makes Nanostructures Unique . . . . . . . . . . . . . . . . . . . . . . 31.2.2 Size Dependence.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2.3 Metal NPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.2.4 Quantum Dots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.2.5 Nanotechnology Imitates Nature. . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.3 From Microelectronics to Nanoelectronicsand Molecular Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.4 Nano in Energy and Clean Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.5 Nanotechnology Tools: Nanometrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151.6 Future Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181.7 Summary.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2 Carbon Nanomaterials: Synthesis, Properties and Applications . . . . . . 23Kyriakos Porfyrakis and Jamie H. Warner2.1 Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.2 Fullerenes and Their Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.2.1 Synthesis of Endohedral Fullerenes . . . . . . . . . . . . . . . . . . . . . . . 252.2.2 Endohedral Metallofullerenes .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.2.3 Endohedral Nitrogen Fullerenes . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.2.4 Molecular Synthesis of Endohedral Fullerenes . . . . . . . . . . . 282.2.5 Purification of Endohedral Fullerenes . . . . . . . . . . . . . . . . . . . . . 292.2.6 Properties and Applications .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292.2.7 Chemistry of Endohedral Fullerenes . . . . . . . . . . . . . . . . . . . . . . 322.2.8 One-Dimensional, Two-Dimensional Arrays

and Beyond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

vii

viii Contents

2.3 Graphene.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362.3.1 Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362.3.2 Properties and Applications .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

2.4 Carbon Nanotubes .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392.4.1 Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402.4.2 Applications.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

2.5 Summary.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3 Carbon Nanotubes: From Symmetry to Applications . . . . . . . . . . . . . . . . . . 47M. Damnjanovic3.1 Introduction: Symmetry of Nanotubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

3.1.1 Configuration of Single-Wall Nanotubes .. . . . . . . . . . . . . . . . . 483.1.2 Symmetry of Single-Wall Nanotubes .. . . . . . . . . . . . . . . . . . . . . 483.1.3 Double-Wall Nanotubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

3.2 Energy Bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513.2.1 Electronic Bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513.2.2 Phonons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

3.3 Interaction Between Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543.3.1 Potential Produced by Nanotube .. . . . . . . . . . . . . . . . . . . . . . . . . . 543.3.2 Interaction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

3.4 Summary.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4 Laser-Based Growth of Nanostructured Thin Films . . . . . . . . . . . . . . . . . . . 59P. Patsalas4.1 Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594.2 Instrumentation and Principles of Pulsed Laser Deposition. . . . . . . . 604.3 Examples and Applications .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.3.1 External Control of Ablated Species andApplication to Ta-C Films [29] . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.3.2 Self-Assembled Nanoparticles intoDielectric-Matrix Films and Superlattices [52, 54] . . . . . . . 71

4.3.3 Control of the Atomic Structure andNanostructure of Intermetallic and GlassyFilms [147] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

5 High Efficiency Multijunction Solar Cells with Finely-Tuned Quantum Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Argyrios C. Varonides5.1 What is a Solar Cell? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865.2 Photo-Currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 875.3 Solution of the Diffusion Equation: n-Region . . . . . . . . . . . . . . . . . . . . . . 885.4 Solution of the Diffusion Equation: P-Region . . . . . . . . . . . . . . . . . . . . . . 895.5 Total Electron and Hole Currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Contents ix

5.6 P-I-N Geometries of Solar Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915.7 A Proposed Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 925.8 The Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 945.9 Current Research Objectives: A Proposed Guideline.. . . . . . . . . . . . . . 955.10 To Probe Further . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

6 Thin Film Deposition and Nanoscale CharacterisationTechniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105Spyridon Kassavetis, Christoforos Gravalidis, and StergiosLogothetidis6.1 Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1056.2 Methods and Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

6.2.1 Thin Film Deposition Techniques . . . . . . . . . . . . . . . . . . . . . . . . . 1066.2.2 Physical Vapor Deposition: Magnetron Sputtering . . . . . . . 1066.2.3 Nanoscale Characterization of Sputtered Thin Films . . . . . 1086.2.4 Wet Deposition Techniques of Thin Films . . . . . . . . . . . . . . . . 125

6.3 Summary: Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

7 Implementation of Optical Characterization for FlexibleOrganic Electronics Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131A. Laskarakis and S. Logothetidis7.1 Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327.2 Optical Characterization of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1337.3 Flexible Organic Electronic Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1377.4 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

7.4.1 Flexible Polymeric Substrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1397.4.2 Barrier Layers for Encapsulation of Devices . . . . . . . . . . . . . . 1447.4.3 Transparent Electrodes (Inorganic, Organic) .. . . . . . . . . . . . . 147

7.5 Conclusions and Perspectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

8 Introduction to Organic Vapor Phase Deposition(OVPDr) Technology for Organic (Opto-)electronics .. . . . . . . . . . . . . . . . . 155Dietmar Keiper, Nico Meyer, and Michael Heuken8.1 Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1558.2 OVPDr Basics and Industrial Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1578.3 OVPDr Deposition of Organic Thin Films and Devices . . . . . . . . . . 158

8.3.1 Single Film Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1588.3.2 Organic Film Morphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1618.3.3 OLED Stack Designs Fabricated by OVPDr

– Cross-Fading .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1638.4 Conclusion .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

x Contents

9 Computational Studies on Organic Electronic Materials . . . . . . . . . . . . . . 171Leonidas Tsetseris9.1 Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1719.2 Computional Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

9.2.1 A Brief Overview .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1739.2.2 First-Principles Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1749.2.3 First-Principles Methods: Limitations and Extensions . . . 1769.2.4 Carrier Hopping Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1789.2.5 Monte Carlo Simulations .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

9.3 Results and Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1849.4 Summary and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

10 Self-Assembly of Colloidal Nanoparticles on Surfaces:Towards Surface Nanopatterning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191Vasileios Koutsos, John Walker, and Emmanouil Glynos10.1 Introduction and Theoretical Background . . . . . . . . . . . . . . . . . . . . . . . . . . 191

10.1.1 Colloidal Particle Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19310.1.2 van der Waals Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19310.1.3 Electrostatic Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19410.1.4 DLVO Theory .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19710.1.5 Electrolyte Concentration Control over Interactions .. . . . . 19810.1.6 Steric Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

10.2 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19910.2.1 Atomic Force Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

10.3 Drying and Immersion Capillary Forces: TheEmergence of Order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20110.3.1 Crystalline Monolayers of Colloidal Silica on Mica . . . . . . 204

10.4 Dewetting Effects: Self-Organisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20510.4.1 Dewetting Structures of Colloidal Magnetite

Nanoparticles on Mica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20610.4.2 Adsorption and Self-Assembly of Soft Colloid

Nanoparticles on Mica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20910.5 Conclusions .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

Contributors

M. Damnjanovic NanoLab, Faculty of Physics, POB 368, Belgrade 11001, Serbia,yqoq@rcub.bg.ac.rs

E. Glynos Institute for Materials and Processes, School of Engineering, Universityof Edinburgh, King’s Buildings, Edinburgh EH9 3JL, UK, eglynos@umich.edu

Ch. Gravalidis Lab for Thin Films – Nanosystems and Nanometrology (LTFN),Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki,Greece, cgrava@physics.auth.gr

Michael Heuken AIXTRON AG, Kaiserstr. 98, 52134 Herzogenrath, Germany,m.heuken@aixtron.com

S. Kassavetis Lab for Thin Films – Nanosystems and Nanometrology (LTFN),Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki,Greece, skasa@physics.auth.gr

D. Keiper AIXTRON AG, Kaiserstr. 98, 52134 Herzogenrath, Germany,D.Keiper@aixtron.com

V. Koutsos Institute for Materials and Processes, School of Engineering,University of Edinburgh, King’s Buildings, Edinburgh EH9 3JL, UK,vasileios.koutsos@ed.ac.uk

A. Laskarakis Lab for Thin Films – Nanosystems and Nanometrology (LTFN),Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki,Greece, alask@physics.auth.gr

S. Logothetidis Physics Department, Lab for Thin Films – Nanosystems andNanometrology (LTFN), Aristotle University of Thessaloniki, 54124 Thessaloniki,Greece, logot@auth.gr

Nico Meyer AIXTRON AG, Kaiserstr. 98, 52134 Herzogenrath, Germany,N.Meyer@aixtron.com

xi

xii Contributors

P. Patsalas University of Ioannina, Department of Materials Science and Engineer-ing, 45110 Ioannina, Greece, ppats@cc.uoi.gr

K. Porfyrakis Department of Materials, University of Oxford, Parks Road, OxfordOX1 3PH, UK, kyriakos.porfyrakis@materials.ox.ac.uk

L. Tsetseris Department of Physics, National Technical University of Athens,15780 Athens, GreeceDepartment of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki,GreeceDepartment of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA,leont@mail.ntua.gr

A.C. Varonides Physics and EE Department, University of Scranton, Scranton,PA, USA, varonides@scranton.edu

J. Walker Institute for Materials and Processes, School of Engineering, Universityof Edinburgh, King’s Buildings, Edinburgh EH9 3JL, UK, John.Walker@ed.ac.uk

J.H. Warner Department of Materials, University of Oxford, Parks Road, OxfordOX1 3PH, UK, jamie.warner@materials.ox.ac.uk