80 research outputs found
Low dose X-ray speckle visibility spectroscopy reveals nanoscale dynamics in radiation sensitive ionic liquids
X-ray radiation damage provides a serious bottle neck for investigating
{\mu}s to s dynamics on nanometer length scales employing X-ray photon
correlation spectroscopy. This limitation hinders the investigation of real
time dynamics in most soft matter and biological materials which can tolerate
only X-ray doses of kGy and below. Here, we show that this bottleneck can be
overcome by low dose X-ray speckle visibility spectroscopy. Employing X-ray
doses of 22 kGy to 438 kGy and analyzing the sparse speckle pattern of count
rates as low as 6.7x10-3 per pixel we follow the slow nanoscale dynamics of an
ionic liquid (IL) at the glass transition. At the pre-peak of nanoscale order
in the IL we observe complex dynamics upon approaching the glass transition
temperature TG with a freezing in of the alpha relaxation and a multitude of
milli-second local relaxations existing well below TG. We identify this fast
relaxation as being responsible for the increasing development of nanoscale
order observed in ILs at temperatures below TG.Comment: 7 pages, 5 figure
Coherent x-ray diffraction study of GaAs nanopillars embedded in air-gapheterostructures
Recent advances in nanofabrication reveal significant impact of
nanostructuring on thermal transport in solids. This paves a way for novel
thermoelectric devices with low thermal conductance. Nanostructured
materials can be fabricated to have dimensions less than the mean free path
of heat carrying phonons. Recently developed fabrication technology of airgap
heterostructures (AGH) enables to create GaAs nanopillars with
controlled length of a few nanometers which can act as ballistic point
contacts for phonons. The AGHs were fabricated using molecular beam
epitaxy combined with in situ local droplet etching technique and ex situ
selective chemical wet etching of a sacrificial layer. Homogeneity and strain
distribution in AGHs is of high importance for the functionality of
thermoelectric device. Despite a strain-free nature of nanopillars grown in
nanoholes, their shape and strain distribution remain to be studied. Using
coherently focused x-rays available at modern synchrotron sources it is
possible to apply the Coherent Diffraction Imaging (CDI) for ab initio
reconstruction of electron density and strain inside an individual
nanostructure. At the same time, conventional reciprocal space mapping
(RSM) can be used to evaluate the defect densities in thin surface layers. In
this contribution we present the results of non-destructive investigation of
AGHs by means of RSM and CDI experiments performed at the P10
Coherence Beamline of PETRA III synchrotron at DESY, Hamburg
Versatile AFM setup combined with micro-focused X-ray beam
Micro-focused X-ray beams produced by third generation synchrotron sources offer new perspective of studying strains and processes at nanoscale. Atomic force microscope setup combined with a micro-focused synchrotron beam allows precise positioning and nanomanipulation of nanostructures under illumination. In this paper, we report on integration of a portable commercial atomic force microscope setup into a hard X-ray synchrotron beamline. Details of design, sample alignment procedure, and performance of the setup are presented
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