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