Research highlights

Atomic force microscopy (AFM)

Interaction of microtubules with the protein tau

Microtubules, constituents of the cytoskeleton, have been studied with AFM in collaboration with the Laboratory of Experimental Genetics and Transgenesis of the Faculty of Medicine. The interaction between microtubules and the protein tau is relevant for the study of Alzheimer�s disease. The AFM topography images elucidated abnormal processes caused by hyperphosphorylation and mutations of the tau protein.


J. Biol. Chem. 281 (35), 25388 (2006)

Metallization of insulin fibrils and peptide nanotubes

Insulin fibrils and other protein nanotubes are metallized by electroless plating or direct interaction with preformed metal colloids, resulting in a biomolecular template that is densely covered with nanometer size metal particles. These structures combine the self-assembling properties of the biomolecular template with the electrical properties of the metal.


Ph.D. thesis M. Gysemans (2009)

Organization of metal particles around an insulin template

Metallized insulin fibrils were investigated with TEM in collaboration with the EMAT group at the University of Antwerp, demonstrating the helical organization of the metal particles on the insulin template. The application of high resolution TEM and electron tomography, in combination with AFM and optical techniques, offers excellent opportunities to study the three-dimensional morphology of metal-protein hybrid structures with unprecedented resolution.


Adv. Mater . 22 (), (2010)

Scanning tunneling microscopy (STM)

Spin-dependent electronic structure of self-organized Co nanomagnets

The herringbone reconstructed Au(111) surface was used as a template for the growth of bilayer Co NPs that have a monodisperse size distribution and that are equidistantly arranged on the Au(111) surface. Our measurements provide direct evidence for the existence of localized d-states of minority and majority character that govern the spin polarization of the NPs below the Fermi level.


New J. Phys. 13, 033030 (2011)

Creating nanostructures with an STM tip

Au adatoms were created on Au(111) with high reproducibility by bringing the STM tip in (near) \ contact with the surface, providing a rather easy means of creating larger nanostructures out of atomic size particles. The electronic structure of the adatoms is dominated by a pronounced resonance below the onset of the Au(111) surface state and is interpreted as a bound state that is split off from the 2D surface state of the Au(111) surface.

Appl. Phys. A 96 (2), 409 (2009)

Electron confinement to Au nanoparticles

By means of ion bombardment of clean Au(111) films, atomically flat nanoparticles of various shapes and sizes were created, ranging from several tens of nm 2 down to only a few nm 2 . Mapping of the local density of states revealed standing wave patterns that could be modeled by particle-in-a-box calculations based on a variational method which can be applied to �2D boxes� of arbitrary polygonal shape.


Nanotechnology 20 (39), 395401 (2009)

Quantum Confinement of Hot Image-Potential State Electrons

Discrete image-potential state (IS) resonances at Co nanoislands on Au(111) are probed using STM. We observe particle-in-box-type standing wave patterns, which is surprising in view of the high energy of the IS electrons when compared to the confining potential imposed by the island edges. Probing high-energy ISs provides a novel route to investigate electronic coupling between nanoislands on surfaces.


Phys. Rev. Lett. 103 (26), 266805 (2009)

Morphology and electron confinement properties of deposited Co clusters

Co clusters are produced in the gas phase and deposited* under controlled ultra-high vacuum conditions** onto clean Au(111). The clusters experience only a restricted flattening and have a multilayered structure exhibiting hexagonal facets, which points to a truncated octahedral shape. Our findings provide direct evidence for the existence of electron confinement effects in the Co clusters stemming from delocalized Co valence electrons.

New J. Phys. 10, 083005 (2008)

* In the cluster deposition apparatus
** Using the home-built ultra-high vacuum transportable vessel

Peeling off graphene from Co nanoparticle covered graphite in a scanning tunneling microscope

Peeling off graphene layers from graphite surfaces with the tip of a scanning tunneling microscope is demonstrated under controlled vacuum conditions. This type of exfoliation is achieved by scanning a Co nanoparticle covered graphite surface with the tip in close proximity.

Carbon 49, 2258 (2011)

Spatial oscillations in the density of states near domain boundaries at Ge(111)2x1

Oscillations appear in the vicinity of boundaries between domains with different atomic arrangements within a limited range of tunneling voltages. We are able to extract the energy versus wave-vector dispersion relation of the spatial oscillations in the local electron density of states. Relying on a tight-binding based model, the observed phenomena are linked to 2D Tamm surface states that are formed within the semiconductor band gap.

Physical Review B 81, 035313 (2010)

Low-dimensional ZnO

Zero-dimensional field emitter based on ZnO quantum dots

Macroscopic field emission measurements reveal that Ga-doped ZnO QDs have a low turn-on field of 1.3 V/µm and a large field enhancement factor up to 10 4 . Kelvin probe force microscopy and scanning field emission probe microscopy are used for mapping at submicrometer scale of the spatial distribution of the work function and the field emission, respectively.

Appl. Phys. Lett. 97, 143102 (2010)

Unexpected optical response of single ZnO nanowires probed using controllable electrical contacts

We demonstrate the transfer characteristics of individual ZnO nanowire FETs, including the gate threshold voltage, hysteresis and even the operational mode, which unexpectedly respond to visible light illumination.

Phys. Chem. Chem. Phys. 13, 6931 (2011)