Tailoring Properties of Adsorbed Metal Layers, Clusters and Molecules by Controlling Dimensionality and Interaction with Substrates
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Date: 07-28-2006
Start Time:
11:00am
End Time: 12:00pm
Speaker: Marko Kralj
From:
Institute of Physics, Zagreb, Croatia
Location: Interschool Lab, 7th floor, Schapiro/CEPSR
Hosted by:
Center for Integrated Science
Abstract:
The electronic structure of materials in the proximity of the Fermi
level largely determines gross properties such as electric and thermal
conductivity, magnetism, strongly-correlated effects, etc. We tend to
create nanometer scaled materials with novel properties, particularly
by seeking the possibilities to tailor their electronic structure
around the Fermi level. The key in achieving this goal is in the
preparation of well defined low-dimensional structures. For the
preparation of new complex structures we explore two distinct
possibilities. The first one regards the use of a transition metal as a
substrate for the growth of noble metal layers. The system of our
choice is Ag/V(100). Vanadium has hybridization gaps with respect to
silver and grants for the quantization of electronic states in the
overlayer. The particularity of this system is extremely good epitaxy
and uniformity of the silver in the limit of the thinnest films, down
to the atomic level. This leads to well defined quantized states and
novel silver properties, e.g. pronounced electron-electron and
electron-phonon correlations, which are to a certain extent limited due
to the finite interaction with substrate electronic states. A quite
different approach regards the use of an ultra thin insulating layer
which largely decouples interactions between adsorbate and the metallic
part of the substrate. The system we use is Al2O3/Ni3Al(111). This
alumina film is characterized by a high degree of perfection due to its
commensurate structure with respect to Ni3Al(111), and consequently
hundreds of nanometers large domains. It has a very complex structure
which is not yet fully understood. More interestingly, this surface can
be used as a template to grow ordered hexagonal arrays of metal
clusters. The 4.16 nm superstructure of the alumina film directly
accounts for the typical periodicities found in the arrays. We report
on our recent investigation of possible arraying effects for magnetic
iron clusters and large copper-phthalocyanine molecules. The distinct
nature of the two investigated systems requires the use of two
different, though complementary, experimental techniques. The first one
is high-resolution angle-resolved photoelectron spectroscopy which is
mainly used in the Ag/V(100) studies. The other one is low-temperature
scanning tunneling microscopy and spectroscopy which is used in the
adsorbate/Al2O3/Ni3Al(111) studies. Both techniques are exploited at
their current limits in order to reveal fine details in the unique
electronic structure of the investigated systems.
Short biography:
Received Ph.D. degree in Physics from Zagreb University in 2003. During the Ph.D. studies main interests were focused to the lifetime issues in low dimensional structures studied by high-resolution ARPES. 2003 postdoc at the University of Bonn, Institute of Physical Chemistry. Areas of interest shifted to low-temperature STM and advanced metallic, molecular and hybrid nano-structures. In 2005 awarded the Alexander von Humboldt fellowship.