Ultra-thin organic films investigated by thermal desorption spectroscopy

Prof. Adolf Winkler
TU Graz Inst. of Solid State Physics
6.5.2009 13:15
HS Physik
Thin organic films have attracted considerable interest due to the rapidly growing field of
organic electronics. One of the key issues is the preparation of well defined organic-
inorganic interfaces. Fundamental studies to this subject have to be carried out under
ultrahigh vacuum conditions, and various analytical techniques can be used to characterise
the organic films. In this talk I will focus on one specific technique, namely thermal
desorption spectroscopy. This method is particularly applicable to get information on the
energetics of the film, to differentiate between mono- and multilayer formation, to get
information on possible decomposition of the organic molecules and to determine the
thermal stability of the film. I will demonstrate the potential of this technique on several
model systems: p-quaterphenyl and p-sexiphenyl on Au(111) and mica(0001), as well as
HAT-CN on Au(111) and Ag(111). In combination with other in-situ techniques, like XPS,
LEED, work function measurements, and ex-situ techniques, like AFM and XRD, a quite
comprehensive understanding of the organic films can be gained.

Reaction kinetics & dynamics of simple molecules on modified Pd(111) surface

Dipl.-Ing. Markus Kratzer
Institut für Festkörperphysik,

TU Graz 28.1.2009 14 Uhr c.t.
HS Physik

A detailed understanding of the interaction of gases with surfaces is crucial for the design of catalysts. Ultra high vacuum conditions provide an environment to study specific aspects of the influence of different surfaces and surface structures on adsorption and desorption processes. Especially metal/metal-oxide interfaces are of interest due to their relevance in the field of heterogeneous catalysis.

Some basic aspects concerning the kinetics and dynamics of gas surface interactions will be discussed exemplarily for the interaction of H2, O2 and CO with modified Pd(111). Ultra thin vanadium oxide-, potassium- and zinc layers served as modifiers. The systems were investigated utilizing various experimental techniques like quadrupole mass spectrometry, time-of-flight spectroscopy, angular distribution measurements and thermal desorption spectroscopy.

The surface structure is of great importance for the reactivity and selectivity towards a
specific reaction. Therefore, additional attention is paid to the stability of the surface under reaction conditions. The structural and chemical stability under reaction conditions was studied by means of low energy electron diffraction, Auger electron spectroscopy and scanning tunnelling microscopy.

Nobel price colloquium

A special double feature will be given on the topics of last years Nobel prices in Physics and Chemistry.

Tuesday 20.01.2009 15:00
Aula

• 15:00 Prof. Dr. Gerhard Ecker,

Faculty of Physics, University of Vienna:Nobel price for Physics 2008:
Symmetrieverletzung in der subatomaren Physik

• 16:00 Coffee break

• 16:30 Prof. Dr. Gottfried Köhler,

Max F. Perutz Labor, University of Vienna:
Nobel price in Chemsitry 2008:
Vorgänge inlebenden Zellen sichtbar machen

Topics in micromachining

Prof. Dr. Heinz H. Busta
Adjunct professor ECE department, University of Illinois at Chicago
Founder, Prairie Prototypes, LLC

Mi, 10.12.2008, 14 Uhr c.t. Hörsaal für Physik

Micro electromechanical systems (MEMS) are gaining acceptance in industrial, medical, military and research applications. Some of the mature uses include sensors such
as pressure, flow, temperature, and acceleration (gyroscopes). Newer applications include bioMEMS for cell sorting and cell/DNA manipulation. MEMS are also being developed to use as a platform technology for the formation of nanodevices.

In this seminar, some microfabricated devices/systems will be described that were
fabricated in our group at the Nanotechnology Core Facility (NCF) at the University of Illinois at Chicago. These include:

• Fabrication of a microswitch using the sacrificial layer technique
• Manipulation of carbon nanotubes (CNTs) for the formation of field emitters and three dimensional integrated circuits (3D-ICs)
• Fabrication of brighter blue light emitting diodes by varying the width of the atomic terraces of c-cut sapphire via varying the off-cut angle from 0 – 34 degrees and high temperature (1400°C) annealing in nitrogen and by embedding 2?m - 5?m tungsten stripes into the sapphire via a damascene process followed by epitaxial lateral overgrowth of n+GaN.

The seminar will conclude by offering suggestions for future MEMS-based research.

Epitaxial Graphene on a metal: Growth, Electronic Structure and Use as Template

Prof. Dr. Thomas Michely, II. Physikalisches Institut, Universität Köln

Do, 6.11.2008, 15 Uhr c.t., Hörsaal für Physik

Epitaxial growth is likely to be the route to cheap graphene suitable for a graphene based electronics. The quality of graphene grown on SiC still suffers from large defect concentrations, low electron mobilities and a hardly controlable number of graphene layers.
Through pyrolysis of hydrocarbons on noble metal surfaces graphene is readily formed. For the dense packed surface of Iridium graphene displays an exceptional structural quality over macroscopic dimensions when grown under proper conditions. If transfer to a suitable substrate becomes possible it could serve as an excellent base material for electronic transport and devices. Using scanning tunneling microscopy, electron microscopies and angle resolved photoemission we studied growth, defects and electronic structure of
graphene on Ir in detail.

Deposition of Ir on graphene on Ir has a surprising side-effect. Highly regular lattices of thermally stable few atom clusters are formed. The binding mechanism of these clusters is uncovered through a combination of scanning tuneling microscopy analysis and density functional theory. At geometrically defined locations within the supercell the graphene rehybridizes form sp2 graphitelike to sp3 diamondlike bonding in between the substrate and
the cluster metal. This binding mechanism makes it plausible that similar cluster lattices might be grown of materials other than Ir, with ensuing potential applications inelectrochemistry, catalysis or for data storage.