Plenarvorträge - DPG-Tagungen

Oberflächenphysik Montag
UHV conditions lowers the density of thiole molecules at the Au(111)
surface which results in an alignment of the thiole molecules parallel to
the Au surface. The focus is on the properties of the line-structure phase
with the lowest surface density [1][2]. Al clusters are evaporated on the
regions of the thiol line-structure in order to investigate where the Al
atoms adsorb. With the STM we find that the Al clusters preferably
adsorb onto the sulphur head of the thiol. Additionally, we investigate
in AFM measurements with Al functionalized tips the forces acting on
different parts of the thiol chain.
[1] Poirer G.E. Langmuir 1999, 15, 1167-1175
[2] Staub R., Toerker M., Fritz T., Schmitz-Hübsch T., Sellam F., Leo
K. Langmuir 1998, 14, 6693-6698
O 14.75 Mo 18:00 Bereich C
Nanoscale Conductivity Spectroscopy on Solid Electrolytes using
an Atomic Force Microscope — •Ahmet Taskiran, Andre
Schirmeisen, Harald Fuchs, Frank Natrup, and Harmut
Bracht — Physikalisches Institut and CeNTech, University of Muenster,
Wilhelm-Klemm-Str.10, 48149 Muenster, Germany
Ion conducting solid materials play an important role as electrolytes
in energy conversion systems, such as batteries and fuel cells, and also in
electrochemical sensors. An important prerequisite for further progress
in this field is a better understanding of the ion transport mechanisms
on microscopic and nanoscopic length scales.
We are using atomic force microscopy (AFM) to measure the ionic
conductivity in nanoscale volumes of dielectric glasses. The AFM is operated
in the non-contact mode in vacuum. After a sudden change of the
tip voltage, the relaxation of the electrostatic force between tip and sample
is measured as a function of time. We measure these relaxation curves
as a function of sample temperatures ranging from 100K to 675K. The
observed relaxation curves are fitted well with a stretched exponential
function and we can determine the activation energy of the conduction
processes of the ions. First results indicate a good agreement of the activation
energies for several prototype ionic glas conductors with values
from macroscopic measurements. This method allows us to study fundamental
processes of ionic transport and is in particular interesting for the
investigation of nanostructured solid electrolytes.
O 14.76 Mo 18:00 Bereich C
Optical phase effects and resonance shift in scattering-type
near-field infrared microscopy — •Thomas Taubner 1 , Fritz
Keilmann 1 , and Rainer Hillenbrand 2 — 1 Max-Planck-Institut für
Biochemie, Am Klopferspitz 18a, 82152 Martinsried — 2 Nano-Photonics
Group, Max-Planck-Institut für Biochemie, Am Klopferspitz 18a, 82152
Martinsried
A scattering-type near-field optical microscope (s-SNOM) detects light
scattered at the sharp tip of a probing needle and allows imaging with
subwavelength resolution, independent of the wavelength used for illumination[1].
We now study amplitude and phase of light scattered from a s-
SNOM’s tip probing a flat SiC sample, at mid-infrared frequencies where
surface phonon polaritons resonantly enhance the tip-sample near-field
interaction [2]. A nanometer-scale variation of the gap width between tip
and sample causes the optical phase to change dramatically and the resonance
to shift. Both effects can be explained by theory that treats the
system as a point dipole (tip) interacting with its image dipole (sample),
in electrostatic approximation. The phase effects and resonance shifts are
not restricted to phonon polariton excitation in polar dielectrics like SiC,
but should be observable also for resonances related to plasmons and
excitons.
[1] T. Taubner, R. Hillenbrand and F. Keilmann, Journal of Microscopy
210, 311 (2003)
[2] R. Hillenbrand, T. Taubner and F. Keilmann, Nature 418, 159
(2002)
O 14.77 Mo 18:00 Bereich C
Investigations on nanocrystals in silicondioxide by atomic force
microscopy — •E. Beyreuther 1 , R. Beyer 1 , K. Walzer 1 , S.
Behrendt 1 , V. Beyer 2 , J. von Borany 2 , J. Weber 1 , and L. Eng 1
— 1 Technische Universität Dresden, Institut für Angewandte Physik, D-
01062 Dresden — 2 Forschungszentrum Rossendorf, Institut für Ionenstrahlphysik
und Materialforschung, PF 510119, D-01314 Dresden
Nanocrystals in SiO2 are promising structures for future optoelectronic
and memory devices. Optimization of the synthesis process needs detailed
information about structure and morphology.
Within the present work SiO2 layers of 100 nm thickness were ther-
mally grown on Si(100). Subsequently Si or Ge nanocrystals were fabricated
within those oxide films by ion implantation and rapid thermal
annealing. Etching in buffered HF-solution with a low rate of 12nm/min
removed the top oxide layer and uncovered the nanocrystals to a certain
depth. The surfaces of several samples, which had undergone varied
implantation and annealing conditions as well as different etching times
were imaged by tapping-mode AFM down to scan sizes of 200x200 µm 2 .
The apparent nanocrystal size and density were found to be dependent
on the synthesis parameters and the position within the oxide layer.
In comparison to TEM investigations of the same structures we discuss
critically the determination of the cluster size.
O 14.78 Mo 18:00 Bereich C
Detection of dopant profiles in silicon by scanning capacitance
microscopy and related techniques: the role of the passivation
layer — •Reinhard Beyer 1 , Elke Beyreuther 1 , Bernd
Schmidt 2 , Stefan Polzin 3 , and Jörg Weber 1 — 1 Technische Universität
Dresden, Institut für Angewandte Physik, D-01062 Dresden —
2 Forschungszentrum Rossendorf, Institut für Ionenstrahlphysik und Materialforschung,
PF 510119, D-01314 Dresden — 3 Fraunhofer-Institut für
Photonische Mikrosysteme, Grenzstrasse 28, D-01109 Dresden
Scanning capacitance microscopy (SCM) was employed for the study
of dopant profiles in silicon test structures. The samples were fabricated
by implantation of boron and phosphorous into n-type silicon. The oxide
mask for the implantation was shaped by photolithography. Hence,
stripe patterns with a size of 2 µm of the implanted region and different
widths of the interregion were obtained. The implantation dose was
5 × 10 12 , 5 × 10 13 and 5 × 10 14 cm −2 for both implanted ions. Samples
with native oxide coverage and with a 7 nm thick silicondioxide layer
were compared in this study. SCM measurements were performed in the
contact-mode. We show, that the contrast of the SCM signal between
differently doped regions depends not only on the dc bias applied during
the scan, but also on charge instabilities and trapping effects. The latter
appeared mostly for samples with native oxide and resulted in hysteresis
effects which could be observed with local dC/dV vs. V spectroscopy.
The charge instabilities are discussed in a MOS-model. The results are
compared with scanning spreading resistance measurements and with
non-contact SCM.
O 14.79 Mo 18:00 Bereich C
Study of particle-substrate interaction by nanomanipulation experiments
with dynamic scanning force microscopy — •Claudia
Ritter 1 , Markus Heyde 2 , and Klaus Rademann 1 — 1 Humboldt-
Universität zu Berlin, Institute of Chemistry, Brook-Taylor-Str. 2, D-
12489 Berlin, Germany — 2 Fritz-Haber-Institute of the Max-Planck-
Society, Faradayweg 4-6, D-14195 Berlin, Germany
We utilise an advanced homebuilt SFM in the dynamic mode, in
conjunction with a special homebuilt software, to perform precise
nanomanipulation experiments. The corresponding experimental technique
should be denoted as Dynamic Surface Modification (DSM), comprising
both the dynamic technique of the SFM, as well as the manipulation
(translation, in-plane rotation, cutting) of structurally unchanged
particles on a given substrate surface. It is easily possible to switch between
imaging mode and DSM mode, enabling the direct manipulation
of nanoparticles under ambient conditions with high precision and simultaneously
studying particle-substrate interaction to give evidence about
motion and tribological values of the sample system. We have successfully
manipulated miscellaneous nanoparticles on surfaces, e.g. antimony
islands, gold islands, tin islands, nanotubes, small latex spheres as well
as cells.
O 14.80 Mo 18:00 Bereich C
In-situ SPM usage at MOVPE-conditions — •Markus
Breusing, Bert Rähmer, Raimund Kremzow, and Wolfgang
Richter — TU-Berlin, Institut für Festkörperphysik, Hardenbergstr.
36, 10623 Berlin
In-situ scanning probe techniques which are applicable in an MOVPE
growth environment to directly give quantitative information about the
nano-scale topography of the sample do not exist up to now.
Developing a SPM for in-situ MOVPE measurements requires a completely
new setup. In comparison to the commercially available SPMsolutions,
a number of additional problems have to be solved. The limited
space in the MOVPE reactors and the high temperature caused by the
thermal conductivity of the carrier gas during growth near the suszeptor
requires a special design of the components of the SPM. On the other