Pit Boye

Hard x-ray nanobeam characterization by coherent diffraction microscopy

We have carried out a ptychographic scanning coherent diffraction imaging experiment on a test object in order to characterize the hard x-ray nanobeam in a scanning x-ray microscope. In addition to a high resolution image of the test object, a detailed quantitative picture of the complex wave field in the nanofocus is obtained with high spatial resolution and dynamic range. Both are the result of high statistics due to the large number of diffraction patterns. The method yields a complete description of the focus, is robust against inaccuracies in sample positioning, and requires no particular shape or prior knowledge of the test object.

Hard X-ray nanoprobe at beamline P06 at PETRA III

We describe the hard X-ray scanning microscope planned for the new synchrotron radiation source PETRA III at DESY in Hamburg, Germany. It is based on nanofocusing refractive X-ray lenses and is designed for two-dimensional mapping and scanning tomography. It supports X-ray fluorescence and (coherent) diffraction contrast, yielding elemental and structural information from inside the sample. Spatial resolutions down to well below 50 nm are aimed for in direct space. A further increase in spatial resolution is expected by applying ptychographic scanning schemes. The optical scheme with a two-stage focusing optic is described.

Non‐destructive and quantitative imaging of a nano‐structured microchip by ptychographic hard X‐ray scanning microscopy

We used hard X‐ray scanning microscopy with ptychographic coherent diffraction contrast to image a front‐end processed passivated microchip fabricated in 80 nm technology. No sample preparation was needed to image buried interconnects and contact layers with a spatial resolution of slightly better than 40 nm. The phase shift in the sample is obtained quantitatively. With the additional knowledge of the elemental composition determined in parallel by X‐ray fluorescence mapping, quantitative information about specific nanostructures is obtained. A significant enhancement in signal‐to‐noise ratio and spatial resolution is achieved compared to conventional hard X‐ray scanning microscopy.

Patterning-induced strain relief in single lithographic SiGe nanostructures studied by nanobeam x-ray diffraction

The continued downscaling in SiGe heterostructures is approaching the point at which lateral confinement leads to a uniaxial strain state, giving high enhancements of the charge carrier mobility. Investigation of the strain relaxation as induced by the patterning of a continuous SiGe layer is thus of scientific and technological importance. In the present work, the strain in single lithographically defined low-dimensional SiGe structures has been directly mapped via nanobeam x-ray diffraction. We found that the nanopatterning is able to induce an anisotropic strain relaxation, leading to a conversion of the strain state from biaxial to uniaxial. Its origin is fully compatible with a pure elastic deformation of the crystal lattice without involving plastic relaxation by injection of misfit dislocations.

Parallel structural screening of solid materials

X-Ray absorption spectroscopy using a microreactor array in combination with an X-ray camera is applied for fast parallel structural screening of a variety of differently prepared supported palladium and copper particles in the as-prepared state and after heat pre-treatments in different gas atmospheres.

Hard X‐Ray Scanning Microscopy with Coherent Diffraction Contrast

A hard x‐ray scanning microscope based on nanofocusing refractive x‐ray lenses is well suited for coherent x‐ray diffraction imaging, in particular for scanning coherent diffraction microscopy also known as ptychography. Using this technique, the complex transmission function of the object can be obtained with a spatial resolution better than that given by the size of the nanofocus. In addition, the full complex wave field in the plane of the sample can be reconstructed simultaneously, allowing for a complete characterization of the illuminating nanobeam. This is illustrated by a ptychogram of a test structure recorded at 24.3 keV.

Nanofocusing refractive X-ray lenses: Fabrication and modeling

Nanofocusing refractive x-ray lenses (NFLs) form the basis of a hard x-ray scanning microscope. They are characterized by their short focal length (~ 10 mm at 15 keV to 25 keV) and large numerical aperture, allowing for the generation of hard x-ray nanobeams even at short distances from a synchrotron radiation source. These optics, made out of silicon by electron beam lithography and subsequent deep reactive ion etching, have been shown to focus hard x-rays down to 50 nm. We have modeled these optics, allowing us to characterize slight aberrations and the wave-field properties in the focus by analyzing the beam profile in the far field.

Hard X‐Ray Nanoprobe based on Refractive X‐Ray Lenses

At synchrotron radiation sources, parabolic refractive x‐ray lenses allow one to built both full field and scanning microscopes in the hard x‐ray range. The latter microscope can be operated in transmission, fluorescence, and diffraction mode, giving chemical, elemental, and structural contrast. For scanning microscopy, a small and intensive microbeam is required. Parabolic refractive x‐ray lenses with a focal distance in the centimeter range, so‐called nanofocusing lenses (NFLs), can generate hard x‐ray nanobeams in the range of 100 nm and below, even at short distances, i. e., 40 to 70 m from the source. Recently, a 47 × 55 nm2 beam with 1.7 ⋅ 108 ph/s at 21 keV (monochromatic, Si 111) was generated using silicon NFLs in crossed geometry at a distance of 47m from the undulator source at beamline ID13 of ESRF. This beam is not diffraction limited, and smaller beams may become available in the future. Lenses made of more transparent materials, such as boron or diamond, could yield an increase in flux of o...

Hard X-ray scanning microscopy with fluorescence and diffraction contrast

Based on nanofocusing parabolic refractive x-ray lenses we have developed and built a hard x-ray scanning microscope that was tested and put to use at beamline ID13 of the ESRF. It can provide a monochromatic hard x-ray nanobeam with lateral extension below 100 nm (down to 50 nm) and a flux up to 109 ph/s in the energy range from 15 to 25 keV. The microscope exploits transmission, fluorescence, and diffraction contrast to obtain local elemental and nanostructural information from the sample. Tomographic scanning yields high resolution elemental maps from the inside of an object. Coherent x-ray diffraction imaging with nanofocused illumination yields images of objects with highest spatial resolution, e. g., 5 nm in a given example.