X-ray physics

X-rays is a form of electromagnetic radiation with a very short wavelength, so they can be scattered by individual atoms. This allows one to study the structure of materials on atomic scale by analyzing X-ray scattering patterns. X-ray scattering has been extensively used to study crystal lattices since the beginning of the 20th century, and the vast majority of crystal structures were characterized by X-ray diffraction. Nowadays, with the development of bright synchrotron sources, we can utilize ultra-bright X-ray beams with a nanosize focus spot and tunable energy. It makes X-rays a very important tool to characterize the crystal structure of novel materials and devices on the nanoscale.

Figure 1: (right) Nanofocused X-ray beam is used to determine the structure of a 3D array of PbS nanopartiles (I. Zaluzhnyy et al., Nano Lett (2017))

X-rays can be produced using so-called X-ray tubes. We have several X-ray units in our laboratory and we use them on a daily basis to characterize the structure of various samples. We also travel to synchrotron sources (such as DESY in Hamburg or ESRF in Grenoble) to perform advanced X-ray scattering experiments. In contrast to the X-ray tubes, the synchrotron radiation has tunable energy, much higher coherence and ability to focus the beam to submicron size. These properties allow us to perform state-of-the-art experiments and develop a deep understanding of the structure and dynamics of our samples. More specifically, we use X-ray photon correlation spectroscopy (XPCS), nanofocused X-ray diffraction, grazing incidence small-angle and wide-angle X-ray scattering (GISAXS and GIWAXS), X-ray reflectivity (XRR), and many other techniques to characterize novel materials that we fabricate in our group or obtain from our collaborators

Figure 2: (left) X-ray diffraction studies of light-induced phase separation in mixed lead-halide perovskites at the Coherence Applications beamline P10 at DESY (Hamburg)

We are free in our choice of samples to study: X-rays can be used to investigate almost any type of materials. Currently, we have the following projects:

• Surface dynamics in organic thin films
• Light-induced phase separation in mixed lead-halide perovskites
• Structure of 3D assembles of nanoparticles (mesocrystals)
• Modification of superconductor material via focused He-ion beam