Cet ouvrage fait partie de la bibliothèque YouScribe
Obtenez un accès à la bibliothèque pour le lire en ligne
En savoir plus

Dispersing and stabilizing semiconducting nanoparticles for application in printable electronics [Elektronische Ressource] = Dispergieren und Stabilisieren von halbleitenden Nanopartikeln zur Anwendung in der druckbaren Elektronik / vorgelegt von Armin Reindl

De
187 pages
Dispersing and Stabilizing Semiconducting Nanoparticles for Application in Printable Electronics Dispergieren und Stabilisieren von halbleitenden Nanopartikeln zur Anwendung in der druckbaren Elektronik Der Technischen Fakultät der Universität Erlangen-Nürnberg zur Erlangung des Grades DOKTOR - INGENIEUR vorgelegt von Armin Reindl Erlangen - 2009 Als Dissertation genehmigt von der Technischen Fakultät der Universität Erlangen-Nürnberg Tag der Einreichung: 29.05.2009 Tag der Promotion: 31.07.2009 Dekan: Prof. Dr.-Ing. Dr.-Ing. J. Huber Berichterstatter: Prof. Dr.-Ing. W. Peukert, Prof. Dr. C. Kryschi Acknowledgments The present work was conducted from 2005 to 2008 at the Institute of Particle Technology of the Friedrich-Alexander-University Erlangen-Nuremberg in collaboration with Evonik Industries, Marl. Several people contributed significantly to this work and therefore need to be recognized here. First, I thank Prof. Dr.-Ing. W. Peukert for giving me the opportunity to accomplish this thesis. No other project could have been more suitable for me. Thank you for your guidance and for always raising the bar. Secondly, I am grateful for all of my colleagues at the institute, especially for the ones I can count among my close friends by now.
Voir plus Voir moins






Dispersing and Stabilizing Semiconducting
Nanoparticles for Application in Printable
Electronics

Dispergieren und Stabilisieren von
halbleitenden Nanopartikeln zur
Anwendung in der druckbaren Elektronik





Der Technischen Fakultät der Universität Erlangen-Nürnberg zur
Erlangung des Grades

DOKTOR - INGENIEUR

vorgelegt von


Armin Reindl


Erlangen - 2009



























Als Dissertation genehmigt von der Technischen Fakultät der
Universität Erlangen-Nürnberg


Tag der Einreichung: 29.05.2009
Tag der Promotion: 31.07.2009
Dekan: Prof. Dr.-Ing. Dr.-Ing. J. Huber
Berichterstatter: Prof. Dr.-Ing. W. Peukert,
Prof. Dr. C. Kryschi
Acknowledgments

The present work was conducted from 2005 to 2008 at the Institute of Particle
Technology of the Friedrich-Alexander-University Erlangen-Nuremberg in
collaboration with Evonik Industries, Marl.

Several people contributed significantly to this work and therefore need to be
recognized here.

First, I thank Prof. Dr.-Ing. W. Peukert for giving me the opportunity to accomplish
this thesis. No other project could have been more suitable for me. Thank you for your
guidance and for always raising the bar.

Secondly, I am grateful for all of my colleagues at the institute, especially for the ones
I can count among my close friends by now.

Additionally, I thank all members of the Research Training Group GRK 1161/1 and
the employees of the Science to Business Center Nanotronics in Marl for the efficient
and pleasant collaboration.

Due to the fact that this was a very interdisciplinary project, I am grateful to
researchers in other departments for their discussions and for allowing me to use their
equipment.

Last but not least I thank my close friends, my family, and especially my wife, Tanja,
for their understanding, patience and support along the way.





Abstract

The costs for fabricating electronic components by conventional methods based on
crystalline silicon are still relatively high. So the development of printing technologies
using semiconducting nanoparticles promises a significant reduction of the production
costs. In the case of applying polymers as substrate material, this approach additionally
enables new applications in the field of flexible electronics, because the advantages of
the flexible production of polymers are combined with the advantages of inorganic
semiconducting materials. Potential applications range from integrated circuits for
consumer products and radio frequency tags to flexible, transparent coatings for
displays. For the realization of printable electronics based on semiconducting
nanoparticles stable dispersions applicable for a printing process are required. The
main objective of this work was to achieve stable suspensions with regard to
aggregation, while conserving the electronic properties of the particles. Thereafter
silicon, zinc oxide, and indium tin oxide nanoparticles were dispersed by various
methods, e.g. stirred media mill, disperser, ultraturrax, in aqueous as well as non-
aqueous media. Different approaches of stabilization were applied, i.e. electrostatic,
steric, electrosteric, and with small organic molecules. The stabilization mechanisms
were investigated in detail by experimental and theoretical methods. In order to
achieve an in-depth insight into the influence of the dispersion process on the
characteristic properties of the semiconducting nanoparticles and thin films thereof
various techniques from particle technology, material science, physics, and chemistry
were conducted. The techniques included e.g. dynamic light scattering, gas sorption
measurements, scanning electron microscopy, transmission electron microscopy,
Raman spectroscopy, infrared spectroscopy, photo-/cathodoluminescence
spectroscopy, thermogravimetric analysis, and X-ray diffraction. The acquired process
know-how was directly implemented into the knowledge chain of the research training
group GRK 1161/1 "Disperse Systems in Electronics". The influence of the dispersion
and stabilization upon the formation of thin films as well as upon the performance of
electronic devices was investigated in close cooperation with the respective project
partners. Thereafter the dispersion and stabilization process was optimized and
adapted to meet the specific requirements of the cooperating projects. With this
approach first demonstrators for a successful application of the zinc oxide
nanoparticles in thin film transistors were accomplished.

Zusammenfassung

Die Herstellung von elektronischen Bauelementen auf konventionellem Wege
basierend auf kristallinem Silizium ist immer noch relativ teuer. So verspricht die
Entwicklung von druckbarer Elektronik eine signifikante Reduktion der
Produktionskosten. Zudem ermöglicht dieser Ansatz durch Verwendung von
Polymersubstraten neue Anwendungsmöglichkeiten im Bereich flexibler Elektronik,
da die Vorteile einer flexiblen Produktion von Polymeren mit den Vorteilen von
anorganischen halbleitenden Partikeln verknüpft werden. Potentielle Anwendungen
reichen von integrierten Schaltungen in Alltags-Produkten über RFID-Tags zu
transparenten Schichten für flexible Displays. Zur Realisierung von druckbarer
Elektronik basierend auf halbleitenden Nanopartikeln sind verdruckbare Dispersionen
erforderlich. Das Hauptziel dieser Arbeit bestand in der Herstellung solcher stabiler
Dispersionen unter Erhaltung der elektronischen Eigenschaften der Nanopartikel.
Dementsprechend wurden Silizium-, Zinkoxid-, und Indiumzinnoxidnanopartikel mit
verschiedenen Methoden, wie z.B. Rührwerkskugelmühle, Disperser und Ultraturrax,
in wässrigen sowie nichtwässrigen Medien dispergiert. Verschiedene Ansätze zur
Stabilisierung wurden angewendet, d.h. elektrostatisch, sterisch, elektrosterisch und
mit kleinen organischen Molekülen. Die Mechanismen der Stabilisierung wurden
sowohl durch experimentelle als auch theoretische Methoden detailliert untersucht.
Um den Einfluss des Dispergierprozesses auf die charakteristischen Eigenschaften der
halbleitenden Nanopartikeln genauer zu beleuchten, wurden verschiedenste Methoden
aus der Partikeltechnologie, den Werkstoffwissenschaften, der Physik und der Chemie
herangezogen. Die Methoden beinhalteten unter anderem Dynamische Lichtstreuung,
Gassorption-Messungen, Rasterelektronenmikroskopie, Transmissionselektronen-
mikroskopie, Raman-Spektroskopie, Infrarot-Spektroskopie, Photo-/Kathodo-
lumineszens-Spektroskopie, Thermogravimetrie und Röntgendiffraktometrie. Das
erlangte Prozess-Know-how wurde unmittelbar in die Wertschöpfungskette des
Graduiertenkollegs "Disperse Systeme für Elektronikanwendungen" implementiert.
Der Einfluss der Dispergierung und Stabilisierung auf die Bildung dünner Schichten
und auf die Performance eines elektronischen Bauelements wurde in enger
Zusammenarbeit mit den entsprechenden Projektpartnern untersucht. Anschließend
wurde der Dispergier- und Stabilisierprozess optimiert und den Anforderungen der
kooperierenden Projekte angepasst. Auf diese Weise gelang es erste Demonstratoren
für eine erfolgreiche Anwendung der Zinkoxidnanopartikel in Dünnfilmtransistoren
bereitzustellen. i
Contents
1 Introduction.............................................................................................................. 5
2 Concept ..................................................................................................................... 7
3 Theoretical background .......................................................................................... 9
3.1 Semiconductors.................................................................................................. 9
3.1.1 Fundamentals of semiconductors............................................................ 9
3.1.1.1 Band structure ............................................................................ 9
3.1.1.2 Direct and indirect semiconductors.......................................... 11
3.1.1.3 Intrinsic and extrinsic semiconductors..................................... 12
3.1.2 Semiconducting materials ..................................................................... 13
3.1.2.1 Crystalline semiconducting elements and compounds ............ 13
3.1.2.2 Amorphous semiconductors..................................................... 15
3.1.2.3 Organic semiconductors........................................................... 15
3.1.2.4 Semiconducting nanostructures ............................................... 16
3.1.3 Thin film transistors based on semiconducting nanoparticles .............. 17
3.2 Dispersion of nanoparticles ............................................................................. 20
3.3 Particle-particle interactions ............................................................................ 23
3.3.1 Van der Waals interaction..................................................................... 23
3.3.2 Electrostatic interaction......................................................................... 26
3.3.2.1 Origin of surface charge........................................................... 26
3.3.2.2 Formation of electrical double layers....................................... 27
3.3.2.3 Interaction of electrical double layers...................................... 33
3.3.3 Born repulsion ....................................................................................... 34
3.3.4 Total interaction energy via DLVO theory ........................................... 35
3.3.5 Solvation, structural and hydration interactions.................................... 36
3.4 Stabilization of nanoparticles .......................................................................... 37
3.4.1 Electrostatic stabilization ...................................................................... 38
3.4.2 Steric stabilization ................................................................................. 39
3.4.3 Electrosteric stabilization 39
4 Experimental section ............................................................................................. 41
4.1 Dispersing methods.......................................................................................... 41
4.1.1 Disperser................................................................................................ 41
4.1.2 Stirred media mill.................................................................................. 41 ii
4.1.3 Ultraturrax ............................................................................................. 43
4.1.4 Ultrasonic finger.................................................................................... 43
4.2 Materials .......................................................................................................... 43
4.2.1 Silicon nanoparticles (Si-NP)................................................................ 43
4.2.2 Zinc oxide nanoparticles (ZnO-NP)...................................................... 44
4.2.3 Indium tin oxide nanoparticles (ITO-NP)............................................. 45
4.2.4 Grinding media...................................................................................... 45
4.2.5 Chemicals and additives........................................................................ 46
4.3 Characterization methods ................................................................................ 46
4.4 Fabrication of thin films .................................................................................. 52
4.5 Fabrication and characterization of thin film transistors ................................. 52
5 Dispersing and stabilizing silicon nanoparticles................................................. 55
5.1 General aspects ................................................................................................ 55
5.2 Dispersion results............................................................................................. 56
5.2.1 Application of the disperser .................................................................. 57
5.2.2 Application of the stirred media mill .................................................... 59
5.3 Theoretical view of the stability of Si-NP ....................................................... 62
5.4 Structure and surface chemistry of Si-NP 70
5.4.1 XRD analysis......................................................................................... 70
5.4.2 Raman spectroscopy.............................................................................. 71
5.4.3 HRTEM measurements......................................................................... 76
5.4.4 Infrared spectroscopy ............................................................................ 77
5.4.5 Elemental analysis................................................................................. 80
5.4.6 Summary ............................................................................................... 81
5.5 Optoelectronic properties of Si-NP ................................................................. 81
5.6 Removal of SiO and functionalization of Si-NP............................................ 85 x
5.7 Dispersing and stabilizing Si-NP in an oxygen-free solvent........................... 90
5.8 Conclusion ....................................................................................................... 98
6 Dispersing and stabilizing zinc oxide nanoparticles......................................... 101
6.1 General aspects .............................................................................................. 101
6.2 Dispersion results........................................................................................... 102
6.2.1 Dispersing and stabilizing ZnO-NP in water ...................................... 103
6.2.1.1 Electrostatic stabilization ....................................................... 103
6.2.1.2 Electrosteric stabilization 104
6.2.1.3 Steric stabilization.................................................................. 105 iii
6.2.1.4 Stabilization with small organic molecules ........................... 107
6.2.2 Dispersing and stabilizing ZnO-NP in organic media ........................ 108
6.2.2.1 108
6.2.2.2 Intrinsic stability in ethylene glycol....................................... 108
6.2.3 Variation of critical dispersion parameters ......................................... 109
6.2.3.1 Application of the disperser ................................................... 109
6.2.3.2 Application of the stirred media mill ..................................... 111
6.2.4 Summary of the dispersion results ...................................................... 113
6.3 Theoretical view of the stability of ZnO-NP ................................................. 113
6.3.1 General approach and important parameters....................................... 113
6.3.2 Electrostatic and electrosteric stabilization......................................... 116
6.3.3 Stabilization with small organic molecules 117
6.3.4 Intrinsic stability in ethylene glycol.................................................... 121
6.4 Surface chemistry of ZnO-NP and adsorption of additives........................... 123
6.4.1 Infrared spectroscopy .......................................................................... 123
6.4.2 Thermogravimetric analysis................................................................ 126
6.4.3 Differential scanning calorimetry........................................................ 130
6.4.4 Summary ............................................................................................. 131
6.5 Influence upon characteristic properties of ZnO-NP thin films .................... 131
6.5.1 Morphology and roughness................................................................. 131
6.5.2 Thermal annealing............................................................................... 133
6.5.3 Electrical performance ........................................................................ 134
6.6 Realization of thin film transistors based on ZnO-NP .................................. 136
6.7 Conclusion ..................................................................................................... 137
7 Dispersing and stabilizing indium tin oxide nanoparticles.............................. 139
7.1 General aspects .............................................................................................. 139
7.2 Dispersion results........................................................................................... 140
7.3 Theoretical view of the stability of ITO-NP.................................................. 141
7.4 Surface chemistry of ITO-NP........................................................................ 143
7.5 Influence upon characteristic properties of ITO-NP thin films..................... 145
7.5.1 Morphology, roughness and thickness................................................ 146
7.5.2 Transmittance ...................................................................................... 147
7.5.3 Conductivity ........................................................................................ 148
7.6 Conclusion ..................................................................................................... 150
8 Generalization of the DLVO models.................................................................. 151 iv
9 Conclusion and outlook....................................................................................... 159
10 Nomenclature ....................................................................................................... 163
11 Literature.............................................................................................................. 169

Un pour Un
Permettre à tous d'accéder à la lecture
Pour chaque accès à la bibliothèque, YouScribe donne un accès à une personne dans le besoin