A delegation of the Korean National Science & Technology Commission (NSTC) Delegation led by Dr. Cha-Dong Kim visited us on 7 December. 
During the Society for the Advancement of Material and Process Engineering (SAMPE) Benelex Student meeting, Niels De Greef is selected for the best presentation award together with a student from UCL and is nominated for the JEC award competition, which will be held in conjunction with the SAMPE Europe Student Meeting in Paris, March 2012. Congratulations!
Correlation between strain and the metal–insulator transition in epitaxial V2O3 thin films grown by Molecular Beam Epitaxy by L. Dillemans et al., 
Deposition and characterization of MgO/Si gate stacks grown by molecular beam epitaxy by Chen-Yi Su et al., Master and PhD Projects
- Synthesis of carbon nanotubes and carpets
- Oxides with a high dielectric constant on Ge and InGaAs
- Electric Field induced Metal - Insulator - Transition
- Magneto-electric properties of oxide heterostructures
- Piezoelectric properties of electro-optical materials
- Nanoparticles for Electron Emission Cancer Tumor Treatment
- Oxide semiconductors with high mobility and low band-gap
- Synthesis and characterization of Li2MPO4F (M=Co, Ni, Mn), Cathode materials for Lithium Rechargeable batteries.
Synthesis of carbon nanotubes and carpets
Our current work mainly involves the synthesis of carbon nanotubes (CNTs) on different substrates.
For instance CNTs are grown directly on the surface of carbon fibers, which will be used in carbon fiber reinforced polymer composites (FRCs).
State-of-the-art FRCs exhibit excellent stiffness and strength. However, their damage resistance/toughness is not yet well established and puts
tremendous restrictions on applications involving fatigue loading. CNTs with their exceptional mechanical properties and high aspect ratio combined
with their low density have demonstrated to significantly improve mechanical properties of nano-reinforced composites.
The controlled placement of CNTs in the polymer matrix has been a critical issue. We tackle this problem by directly growing CNTs on the surface of carbon fibers.
Our main goal is to gain fundamental insight into the problems of network formation and interaction between hierarchical levels, and how this can lead to a
toughening effect in nano-engineered epoxy matrices and their FRCs.
Vertically aligned CNTs – so called CNT carpets or forests – are grown on Si substrates. We use a buffer layer of Al2O3 prepared by sol-gel and
spin-coated on Si. A thin film of Fe grown by MBE is used as catalyst.
We also explore their potential use in various applications, such as for Li-batteries, sensors, fibers etc.
Faculty/research group : Faculty of Science / Faculty of Engineering
Daily supervision : Edina Couteau, Niels Degreef
Graduating option : Master in Physics / Master in Nanoscience and Nanotechnology
Type of work : Experimental / Simulations
Number of students : 1-2
Oxides with a high dielectric constant on Ge and InGaAs
Dielectric oxides are critical elements
in many electronic devices for logic applications
such as metal-oxide-semiconductor field-effecttransistors
(MOSFET) as well as in several
memory devices (FLASH and DRAM). The
requirements (band gap and dielectric constant) for
the different applications (F=Flash, L=Logic,
D=Dram) are illustrated in the adjacent Figure.
From a fundamental viewpoint, one of the key
design challenges in this field, is to create dielectrics heterostructures with a very high
dielectric constant while maintaining a very low leakage current. The appropriate
materials currently do not exist! Artificial structures with novel electric dipole
configurations will be designed, developed and tested during this project1.
From an experimental point of view, these oxides will be integrated with semiconductors
such as Ge and InGaA in capacitor and transistor structures2. One of the major issues
that prevents the use of Ge and InGaAs MOSFETs today, is the large amount of
electrically active defects at the interface. By controlling the interface structure and
chemistry as well as the interatomic stacking sequence using molecular beam epitaxy,
novel surface passivation strategies will be developed.
This project can be executed both from a fundamental viewpoint or from a more
experimental viewpoint. The activities will take place in the framework of a European
collaboration with industrial partners such as IBM and ST.
1 EM Vogel, Nature Nanotechnology, 2, 25 (2007); W. Andreoni et al, Appl. Phys. Lett., 96, 062901 (2010).
2 YN Sun et al., IEEE Elec. Dev. Lett., 28, 473-475 (2007); C. Marchiori et al., J. Appl. Phys., 106, 114112 (2009).
Faculty/research group : Faculty of Science/Lab. of Solid State Physics and Magnetism
Daily supervision : Dr. Mariela Menghini, Drs. Tomas Smets
Graduating option : Master in Physics / Master in Nanoscience and Nanotechnology
Type of work : Experimental / Simulations
Number of students : 1-2
Electric Field induced Metal - Insulator - Transition
For non-volatile memory (NVM)
applications, the goal is to change from flash
technology towards more compact and scalable
designs using alternative mechanisms. Phase change
(PCM) and resistive switching memories (RRAM)
are two popular approaches. While many
“switching” mechanisms are proposed, we focus here
on purely electronic phase transition between an
insulating and a metallic state. The adjacent Figure
shows the resistivity changes versus temperature for
the Pr(Ca,Sr)MnO3 compound.
From a fundamental viewpoint, one of the key
challenges is that the metal insulator transition
(MIT) in correlated electron systems is still not fully
understood (Mott vs Peierls transition). In addition,
novel materials and/or heterostructures must be designed1 and tested whereby the gap
opens far above room temperature, and far from “disturbing” structural phase transitions.
From an experimental point of view, MIT oxide thin films will be deposited using sol-gel
and molecular beam epitaxy methods. The metal-insulator transition will be determined
as function of applied electric fields and temperature. Finally they will be integrated into
functional devices such as memory elements and varistors2.
This project can be performed both from a fundamental and from an experimental
viewpoint. The activities take place in the framework of a collaboration with industrial
partners.
1 J Cao et al., Nature Nanotechnology 4, 732, (2009); M Tomczak et al., EuroPhysics Letters, 86, 37004 (2009).
2 MJ Lee, Advanced Materials, 19, 3919 (2007); BJ Kim et al., IEEE Electron Device Letters 31, 14 (2010).
Faculty/research group : Faculty of Science/Lab. of Solid State Physics and Magnetism
Daily supervision : Dr. Mariela Menghini, Drs. Leander Dillemans
Graduating option : Master in Physics / Master in Nanoscience and Nanotechnology
Type of work : Experimental / Simulations
Number of students : 1-2
Magneto-electric properties of oxide heterostructures
In many applications of magnetic materials – as in hard
disk storage – a large magnetic field is needed to revers
the magnetization. However the application of a large
magnetic field required the integration of bulky electromagnets,
which is not easy to achieve. A remedy is
offered by magneto-electric materials, where there is an
intimate coupling between the magnetic spins and the
electric dipoles. Hence the application of an electric
field leads to a magnetization reversal. And vice versa,
the application of a magnetic field leads to a
ferroelectric dipole moment.
From a fundamental viewpoint, one of the key design challenges is that this magnetoelectric
coupling is rather weak leading to unpractically small effects. A strong magnetoelectric
material operating above room temperature does not exist today! Artificial
structures with a strong coupling between the magnetic spins and electric dipoles -- such
as the one illustrated in the adjacent figure -- must be designed, developed and tested1.
From an experimental point of view, magneto-electric oxide thin films will be deposited
using sol-gel and molecular beam epitaxy methods. The magneto-electric coefficients
will be determined as function of applied magnetic and electric fields, both as a function
of frequency and temperature. Finally they will be integrated into functional devices such
as tunnel junctions as well as electric field and magnetic field tunable microwave filters2.
This project can be performed both from a fundamental or an experimental viewpoint.
The activities will take place in the framework of a collaboration with industrial partners.
1 RJ Zeches et al., Science 326, 5955, 977 (2009); AJ Hatt et al., Physical Review B81, 054109 (2010).
2 P Maksymovych et al., Science, 324, 5933, 1421 (2009); AS Tatarenko et al., J. Electroceramics 24, 5 (2010).
Faculty/research group : Faculty of Science/Lab. of Solid State Physics and Magnetism
Daily supervision : Dr. M. Menghini, Dr. S. Thayumanasundaram, Drs. L. Dillemans
Graduating option : Master in Physics / Master in Nanoscience and Nanotechnology
Type of work : Experimental / Simulations
Number of students : 1-2
Piezoelectric properties of electro-optical materials
Context:
In recent years there has been spectacular progress in the development of novel organic materials for electro-optical applications.
These materials have a specific structural construction that induces a permanent charge distribution (a dipole) across the molecule. This
non-centrosymmetric construction is illustrated in the adjacent Figure for a porphyrine derivate whereby both the charge difference and the
distance between the positive and negative charge centers determine the magnitude of the electric dipole moment. The electric field that
appears in the molecule can couple easily with external electromagnetic waves (electro-optical EO effect) or mechanical forces (piezo-electric PE effect).
Recently large EO coefficients have been measured in these new organic materials. Since the EO and the PE coefficient are in principle related
to each other via the same dipole moment it is expected that these materials should have a large PE coefficient. If a significant PE coefficient
is found then this opens the door to many potential applications in sensors and actuators.
Objective:
Determine the PE coefficient of organic materials with a large EO coefficient.Work to be done:
Choose a few interesting organic compounds. Make thin films of these compounds. Determine the electrical properties and the PE coefficient.Expected results:
Proof of principle experiment to determine whether indeed a large PE coefficient is found.
Faculty/research group : Faculty of Science
Daily supervision : Edina Couteau, Mariela Menghini
Graduating option : Science/Nanoscience or Engineering/Nanotechnology
Type of work : Experimental
Number of students : 2
Nanoparticles for Electron Emission Cancer Tumor Treatment
Many different chemical and physical routes
are currently followed of the treatment of tumor cells. One
such method is based on the natural emission of Auger
electrons from radionuclides such as 123I, whereby one decay
releases about 15 electrons with an average energy of 7.5
keV. This methods has several disadvantages and an
alternative method is to use photo-excited electrons from K
and L shells under x-ray radiation as illustrated in the
adjacent Figure. These electrons will be emitted from a
nanoparticle (NP).
From a fundamental viewpoint, one of the key challenges is
to determine the optimal size, shape and material composition of the NP that will lead to
the maximum amount of double DNA strand breaks for the lowest irradiation dose. For
this, novel alloy core-shell nanoparticles will be designed1 -- as illustrated in the Figure below
-- and their electron emission spectrum will be simulated numerically.
From an experimental point of view, alloy NP will be synthesized in a core-shell
structure using different methods2. In the next step, the NP will be functionalized using
antibodies that bind to cancer cells. Finally, the functionalized NP will be dispersed in
cancer cel cultures, their uptake will be determined and the therapeutic effect of the xray
irradiation on the tumor growth rate will be determined.
This project can be performed both from a fundamental as well as from a practical
viewpoint. The activities will take place in the framework of a collaboration with
industrial partners.
1 F Van den Heuvel et al., Phys Med Biol, in press;
2 S Pal et al., J. Nanoscience and Nanotechnology 10, 775 (2010).
Faculty/research group : Faculty of Science/Lab. of Solid State Physics and Magnetism
Daily supervision : Dr. Edina Couteau
Graduating option : Master in Physics / Master in Nanoscience and Nanotechnology
Type of work : Experimental / Simulations
Number of students : 1-2
Oxide semiconductors with high mobility and low band-gap
Semiconductor technology
combines two very different and incompatible
materials, namely simple semiconductors and
oxides. The former (Si, Ge, InGaAs) are essential
for efficient carrier transport while the latter
enable various functionalities (such as dielectric,
ferroelectric, piezoelectric, ...). These material
incompatibilities always lead to sub-optimal
properties and devices. There exists however a
large class of oxide semiconductors with a carrier
mobility around 100 cm2/Vs much larger than amorphous Si.
From a fundamental viewpoint, there are two key challenges, namely to design1 materials
and heterostructures wherein first a higher carrier mobility is possible and second
whereby the band-gap can be reduced to the range 0.7 - 2 eV. Oxide compounds that
fulfill these goals currently do not exist! In particular the options related to suboxides
have not been explored much.
From an experimental point of view, oxide semiconductors will be grown using sol-gel
and molecular beam epitaxy. After growth they will be annealed at high temperature
under different conditions. The electrical properties (resistivity, carrier mobility, bandgap)
will be determined as a function of temperature. Finally they will be combined with
oxide dielectrics into functional capacitor and transistor structures2.
This project can be performed both from a fundamental and from an experimental
viewpoint. The activities will take place in the framework of a collaboration with
industrial partners.
1 B. Falabretti et al., J Applied Physics 102, 123703 (2007); J Robertson, J Non-Crystalline Solids 354, 2791 (2008).
2 H. Ohta et al., Advanced Functional Materials, 13, 139 (2003); K. Nomura et al., Science, 300 1269 (2003).
Faculty/research group : Faculty of Science/Lab. of Solid State Physics and Magnetism
Daily supervision : Drs. Leander Dillemans
Graduating option : Master in Physics / Master in Nanoscience and Nanotechnology
Type of work : Experimental / Simulations
Number of students : 1-2
Synthesis and characterization of Li2MPO4F (M=Co, Ni, Mn), Cathode materials for Lithium Rechargeable batteries.
Lithium-ion batteries are the systems of choice,
offering high energy density, flexible and light weight design,
and longer lifespan than comparable battery technologies. The
cycle-life and life time are dependent on the nature of the
interfaces between the electrodes and electrolyte, whereas
safety is a function of the stability of the electrode materials
and interfaces. Lithium metal phosphates (LiMPO4, M= Co, Ni,
Fe, Mn) have now been widely recognized as a new generation
of cathode materials that can offer safety, power and energy to
satisfy the fast growing large platform applications. Fluorides,
however have been expected to be useful as high voltage
cathodes because the electro negativity of fluorine is greater
than that of oxide. The preliminary results of discharge profiles
of Li2MPO4F (M = Ni and Co) show high operation voltage (≥5 V) and large theoretical
capacity (310 mAh/g) (if 2Li+ can be reversibly removed).
From a fundamental viewpoint, the key design challenge1 is to create materials
(fluorophosphates see adjacent Figure) that allow for i) a better strain accomodation upon
charging/discharging, ii) higher storage capacity, iii) low interface resistances, iv)
chemical stability and v) high temperature stability.
From an experimental point of view, Li2MPO4F (M = Co, Ni) will be synthesized2 either
by solid state reaction or sol-gel method. Thermal and structural properties will be
investigated by TG/DTA, XRD, FTIR etc., The electrical properties (Impedance,
Dielectric) will be determined as a function of temperature. Finally complete battery coin
cells will be fabricated using these cathode materials and tested.
This project can be performed both from a fundamental and from an experimental
viewpoint. The activities will take place in the framework of a collaboration with
industrial partners.
1 KS Kang et al, Science, 311, 977 (2006); A. Patil et al., Materials Research Bulletin, 43, 1913 (2008);.
2 S. Nishimura et al., Nature Materials, 7, 707 (2008); MA Roscher et al., J of Power Sources, 195, 3922 (2010).
Faculty/research group : Faculty of Science/Lab. of Solid State Physics and Magnetism
Daily supervision : Dr. Savitha Tayumanasundaram, Dr. Edina Couteau
Graduating option : Master in Physics / Master in Nanoscience and Nanotechnology
Type of work : Experimental / Simulations
Number of students : 1-2
