Development of silicon nanoparticles with tailored surface properties [Elektronische Ressource] / vorgelegt von Carla Cimpean

Sujets

• Physik

Informations

• Publié par: friedrich-alexander-universitat_erlangen-nurnberg
• Publié le: 01 janvier 2008
• Nombre de lectures: 9
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

Development of Silicon Nanoparticles
with Tailored Surface Properties
Der Naturwissenschaftlichen Fakultät
der Friedrich-Alexander-Universität Erlangen-Nürnberg
zur
Erlangung des Doktorgrades
vorgelegt von
Dipl.-Ing. Carla Cimpean
aus Gherla (Rumänien)Als Dissertation genehmigt von der Naturwissenschaftlichen Fakultät
der Universität Erlangen-Nürnberg
Tag der mündlichen Prüfung: 14. Oktober 2008
Vorsitzender der
Promotionskommision: Prof. Dr. Eberhard Bänsch
Erstberichterstatter: Prof. Dr. Carola Kryschi
Zweitberichterstatter: Prof. Dr. Dirk GuldiTable of Contents
Table of Contents.................................................................................................... i
List of abbreviations.............................. iii
1 Introduction .........................................................................................................1
2 Theoretical Background......................4
2.1 Fundamentals of Nanoparticles ...................................................................4
2.1.1 Properties of ......5
2.1.2 Volume and Surface Effect in Nanoparticles............................................8
2.1.3 Interactions between Nanoparticles........................11
2.2 Nanoparticles and Quantum Confinement ...............................................13
2.3 Synthesis of Silicon Nanoparticles .............................................................18
2.4 Functionalization of Silicon Nanoparticles................21
2.4.1 Thermally Induced Hydrosilylation........................22
2.4.2 Silanization............................................................................................25
2.5 Investigation Methods................26
2.5.1 Fourier Transform Infrared Spectroscopy and Diffuse Reflectance
Infrared Fourier Spectroscopy (FTIR and DRIFTS) ......................26
13
2.5.2 Solid-State TOSS C Nuclear Magnetic Resonance Spectroscopy (TOSS
13
C NMR).......................................................................................................30
2.5.3 Scanning Tunneling Microscopy / Spectroscopy (STM / STS)...............34
2.5.4 High Resolution Transmission Electron Microscopy (HRTEM) ............37
2.5.5 Photoluminescence Spectroscopy ..........................................................39
2.5.5.1 Determination of Photoluminescence Quantum Yield......................43
3 Experimental......................................................................................................44
3.1 Materials.....44
3.2 Hydrosilylation of SiNPs with Phenyl acetylene .......................................47
i3.3 Optimization of the HF Etching Process .................................................. 47
3.4 Determination of the Photoluminescence Quantum Yields of
2-Ethenylpyridine-terminated Siqdots ........................................................... 48
3.5 Hydrosilylation Experiments of Siqdots................... 49
3.6 Silanization Experiments........................................................................... 50
3.7 Sample Preparation and Measurements.................. 51
4 Results and Discussion...................................................................................... 54
4.1 Investigation of Styrenyl-terminated SiNPs............. 54
4.1.1 DRIFTS Measurements......................................................................... 54
13
4.1.2 Solid-state TOSS C NMR Results...................... 57
4.1.3 STM / STS Investigations..... 58
4.1.4 HRTEM Characterization...................................................................... 59
4.2 FTIR Spectroscopy of Etched Siqdots ...................................................... 60
4.3 Characterization of Functionalized Siqdots with 3-Ethynylthiophene ... 62
4.3.1 FTIR Analysis....................................................... 62
4.3.2 STM / STS Characterization ................................................................. 63
4.3.3 PL Results............................. 64
4.4 2-Ethenylpyridine-terminated Siqdots in Comparison with
4--Siqdots ........................................................... 66
4.5 Characterization of Stabilized Siqdots by Silanization............................ 80
4.5.1 Siqdots silanized with TDS ................................................................... 81
4.5.2 Siqdots with CDVS 87
5 Summary ........................................................................................................... 91
6 Zusammenfassung ............................................................................................ 93
References............................................................................................................ 96
iiList of abbreviations
SiNPs Silicon nanoparticles
Siqdots Silicon quantum dots
PMS Particle mass spectrometer
FTIR Fourier transform infrared spectroscopy
DRIFTS Diffuse reflectance infrared Fourier transform
spectroscopy
TOSS Total oppression of spinning sidebands
NMR Nuclear magnetic resonance
TMS Tetramethylsilane
STM Scanning tunneling microscopy
STSspectroscopy
HRTEM High resolution transmission electron microscopy
WPOA Weak-phase-object approximation
PL Photoluminescence
PLE Photoluminescence excitation
LCAO-MO Linear combination of atomic orbitals molecular orbital
PVDF Polyvinylidene fluoride
PFA Perfluoroalkoxy
LUMO Lowest unoccupied molecular orbital
TDS Trichlorododecylsilane
APTES (3-Aminopropyl)triethoxysilane
CDVS Chlorodimethylvinylsilane
O.D. Optical density
iii1 Introduction
1 Introduction
Today, crystalline silicon forms the basis of all electronic applications in
micro- and optoelectronics. The high availability and the low cost of this material,
as well as the specific electronic properties allow the manufacture of integrated
electronic devices at a very large scale. For optoelectronic applications, silicon
played a relatively minor role because of its inefficient light emission. But this
1
changed with the discovery of photoluminescence from porous silicon by Canham ,
and numerous studies were initiated connecting the emission from nanoporous
silicon to quantum confinement. As the essential consequence, silicon nanoparticles
(SiNPs) have gained in importance for the development of optical and electronic
applications. Nanoscale silicon is becoming more and more important for
electronics in term “nanoelectronics”. It is the general assumption that
nanoelectronics will follow – and already has in certain aspects – microelectronics,
when further miniaturization and higher integration leads to ever smaller feature
2
size of the devices on a chip .
The first reference to theoretical nanotechnology was given by Richard
Feynmann on December 29, 1959 in Pasadena in the after-dinner talk lecture
3
“There’s a plenty of room at the bottom” . He was considered as a visionary,
because the essential ideas enunciated in his speech are now technically feasible.
The shortest and most complete definition of nanotechnology is given by the US
4
National Science and Technology Council which states: “The essence of
nanotechnology is the ability to work at the molecular level, atom by atom, to create
large structures with fundamentally new organization. The aim is to
exploit these properties by gaining control of structures and devices at atomic,
molecular, and supramolecular levels and to learn to efficiently manufacture and
use these devices”. In short, nanotechnology is the ability to build micro and macro
materials and products with atomic precision.
11 Introduction
The synthesis of nanoscale materials is of academic and industrial
importance. The approaches for the fabrication of the nanomaterials fall in two
categories: bottom-up and top-down. Bottom-up manufacturing involves the
building of structures, atom-by-atom or molecule-by-molecule while the top-down
manufacturing starts with a larger piece of material that will be etched, milled or
machined to get a nanostructure from it by removing material.
A molecular level understanding of the chemistry involved in the preparation
of these scale-reduced materials is crucial for the rational fabrication of new
commercially viable devices with tailored functions. Particularly significant
examples are the quantum confinement effects observed in semiconductor
nanoparticles, where it has been shown that careful control of particle size can shift
the maximum visible luminescence intensity to higher energy, a property that has
been exploited in the development of sensors, computer displays, and bioinorganic
constructs. The photoluminescence properties depend also on the medium
surrounding the nanocrystals. Therefore, a clear understanding of the effect of
aspects of the surrounding medium on the photoluminescence properties is
important for potential device applications.
The objective of this work was directed towards functionalizing the silicon
nanoparticles with suitable organic molecules to produce surfaces with tailored
optical and structural properties which have to be characterized using microscopic
and spectroscopic techniques. The photochemical stability of the functionalized
silicon nanoparticles is the prior condition f