Controlled nanostructuring of a gold film covered with alkanethiol SAM by low energy cluster implantation
Size matters in scandium doped copper clusters
Ostwald ripening - Movie
Doped AunX+ clustersMaster Theses
Clusters and Laser Spectroscopy
Laser spectroscopy and mass spectrometry of doped clusters
How does the composition of doped silicon clusters influence their geometry and electronic structure?
We produce beams of mixed clusters of a few up to several hundreds of atoms with a laser vaporization source,
and study their properties with laser spectroscopy and mass spectrometry. With deep infrared spectroscopy we can
identify vibrational transitions that are characteristic for the cluster geometry, while visible light
(or near infrared) spectroscopy identifies the electronic transitions. The employed technique is so-called
action spectroscopy where absorption of laser light results in dissociation, fragmentation and/or ionization.
For this research we have several laser systems available providing nanosecond pulsed light with wavelengths
tunable between 195 and 2000 nm. For the absorption of infrared light, through the vibrational degrees of freedom
in a frequency range from 100 cm-1 up to 500 cm-1, we move to the free electron laser FELIX (Free Electron Laser
for Infrared eXperiments) of the FOM Institute for Plasma Physics Rijnhuizen (Nieuwegein, Nederland).
We also plan to perform measurements of the magnetic moments of transition metal doped silicon clusters.
Hereto the current cluster setup will be extended with a Stern-Gerlach magnetic deflector. Part of the
thesis work can be devoted to the design of this deflector and to simulations of the cluster’s flight
path under influence of the magnetic field.
Promoter: Prof. Peter Lievens, Dr. Ewald Janssens
Daily supervision: Pieterjan Claes, Jorg De Haeck, Hay Thuy Le, Dr. Soumen Bhattacharyy, Dr. Sandra Lang
Type of work: experimental and/or simulations
Clusters for catalysis
Catalytic technologies are at the core of more than 80 % of the processes in the chemical industry today.
Improvement of their per¬formance is expected to have a major impact in the near future in the crucial
strategic issues of environment and renewable energy. Most of the catalysts nowadays consist of highly
dispersed very small metallic (nano)¬particles supported on oxide supports. Two key parameters that are
directly influencing their performance are the size of the metallic particles and the nature of the support.
We have recently implemented a new physical method of producing very homogeneous model catalysts based
on size-selected gas phase clusters. By studying their catalytic properties in collaboration with catalysis
groups, we aim at understanding the role of the size and support on the catalytic activity with as ultimate
goal the design of novel high performance catalysts. The goal of this thesis research is to produce series
of size-selected Au, Pd, and Pt clusters using the laser vaporization cluster source (between few atoms and
4.0 nm) and deposit them onto different types of thin oxide layers. You will characterize these transparent
materials by grazing incidence X-ray diffraction and by atomic force and scanning tunneling microscopies
(AFM and STM). In a second stage their catalytic activity will be monitored by fluorescence microscopy detection
techniques using reactive fluorescent probe molecules.
Promoter: Prof. Peter Lievens
Daily supervision: Dr. Didier Grandjean, Christian Romero
Type of work: experimental
Magnetron sputter source for cluster production and deposition
Nanoparticles and clusters can be produced in many different chemical and physical ways.
Advanced technologies have recently been developed to facilitate cluster deposition in
order to study properties of clusters and cluster-assembled systems on surfaces. As physical
properties (magnetic, optical, superconducting, etc.) of these nanometer sized particles are
strongly size dependent, controlling the size of the produced clusters is of utmost importance.
In this thesis you will optimize a new cluster source for cluster production and deposition,
based on magnetron sputtering and gas aggregation. In this type of source, atoms are sputtered
from the target material by an Ar plasma, while a stream of He gas carries the atoms into a
liquid nitrogen cooled aggregation tube. The cluster growth takes place in this growth tube
after which the formed clusters are expelled into high vacuum where they can land on a surface.
This type of cluster source is able to generate an intense beam of clusters with sizes ranging from
a few atoms to 10 nm. Your work will consist of exploring different ways to control and tune the
size of the produced clusters. There are several ways to tune the cluster size, e.g., by varying
the position of the sputter head in the growth tube (the longer the distance, the larger the clusters)
or by controlling the flow of Ar and He gas. Mass selection of the cluster beam could even be achieved
by implementing a quadrupole mass selector. The size distribution of the produced clusters can be
determined by time-of-flight mass spectrometry. You will also study in detail the size and shape of
clusters of different materials after deposition on a substrate by scanning probe microscopy.
Promoter: Dr. Ewald Janssens, Prof. Peter Lievens, Prof. Margriet Van Bael
Daily supervision: Christian Romero, Dr. Sandra Lang, Dr. Stijn Vandezande
Type of work: experimental
Zero-energy SIMS
Due to the ongoing scaling of semiconductor structures (Moore’s law), the position of dopant atoms which
determine the electrical properties of a device becomes more important. Until now, secondary ion mass
spectrometry (SIMS) is used to determine these dopant profiles because of its high sensitivity. However,
quantitative depth profiles with a high depth resolution (sub-nm) are becoming more and more challenging due
to the ion-substrate interaction.
Zero-energy SIMS aims at eliminating these drawbacks by replacing the ions by a combination of
electrons and a reactive gas mixture, and by ionizing the emitted species by laser post-ionization.
First results are very promising. In this thesis subject the technique will be optimized further,
with emphasis to the fundamental etching and laser post-ionization mechanisms.
(Research in collaboration with Imec.)
Promoter: Prof. Peter Lievens, Prof. Wilfried Vandervorst
Daily supervision: Nico Vanhove
Type of work: experimental
Unraveling the quantum mechanical properties of nanoparticles with scanning tunneling microscopy
Nanoparticles, providing the bridge between the atomic and the bulk level, attract a lot of attention
in solid state physics. Their properties do not simply scale with their size and cannot be readily predicted.
A profound knowledge of their behavior is of crucial importance for fundamental physics, but also, e.g., for
the operation of future nanoelectronic circuits and data storage media. Controlled preparation of nanoparticles
on a substrate allows probing their physical properties with high spatial and energy resolution by means of
scanning tunneling microscopy (STM) and spectroscopy (STS).
For this thesis project, you will create nanoparticles (clusters) in the gas phase by means of condensation
of evaporated atoms, and deposit them on atomically flat substrates. The central goal of this research project
is a systematic investigation of the size dependence of the electronic properties of these deposited clusters by
STS. More precisely, you will study the properties of individual nanoclusters for which the interaction with
the substrate is minimized. This can be achieved by depositing the nanoclusteres on metallic substrates that are
covered with a thin NaCl layer that acts as a tunnel barrier and basically eliminates the interaction with the
underlying substrate.
Quantum-mechanical confinement phenomena and Coulomb charging effects are expected to play a dominant
role because of the finite size of the nanoclusters, while also the particle shape will play a prominent role.
Promoter: Dr. Ewald Janssens, Prof. Peter Lievens, Prof. Margriet Van Bael, Prof. Chris Van Haesendonck
Daily supervision: Koen Lauwaet, Koen Schouteden
Type of work: experimental
Nano Biophysics
Nanoclusters for protein binding
Recent research trends combine physics at the nanometre scale with biological systems
such as DNA or proteins. Relevant examples are protein microarrays for the simultaneous
detection of many different proteins for early diagnosis of specific diseases. To optimise
the density of proteins, a new generation of protein 'nanoarrays' is being developed.
A possible route towards dense protein nanoarrays is to use atomic clusters on a surface
to immobilise individual proteins. The purpose of this thesis research is to create and
optimise patterns of atomic clusters on biocompatible surfaces, which will in a later
stage be used to bind individual proteins. You will use a laser vaporization cluster
source to produce gold clusters of only a few nanometer in size and deposit them on
different surfaces. You will investigate the resulting cluster patterns by scanning
tunnelling and atomic force microscopy. You will functionalize the clusters for site
specific binding of proteins and systematically check every step in this process by
different methods including atomic force microscopy, quartz crystal microbalance, ...
For the surface functionalization, you will also use the experimental facilities at Imec.
Promoter: Prof. Margriet Van Bael, Prof. Carmen Bartic
Daily supervision: Tobias Peissker, Dr. Johan Snauwaert
Type of work: experimental
Thesisonderwerpen: Vaste-stoffysica op nanometerschaal
