Speaker
Prof.
Victor Asadchikov
(FSRC "Crystallography and photonics" RAS)
Description
Not fully ordered system (not crystals) are widespread in the surrounding nature, as well as in a number of new technologies. It seems natural to want to know what is inside, how different natural formations are arranged, or how accurately we created what we wanted. X-ray study can help us in this. As is known, X-ray structural analysis allows to reveal the internal structure of crystals up to the location of individual atoms. However, in the absence of complete orderliness, other phenomena related to the use of x – rays can be used, such as reflection, absorption and scattering.
X – ray reflectometry is a method of investigation of layered systems with smooth section boundaries compared to the used radiation length. It is important to note that the analysis of the radiation scattering allows to quantify the roughness of the surface under study in a sufficiently wide range of spatial frequencies. It is shown that for a number of substrate materials as a result of their processing it is possible to achieve roughness at the level of one Angstrom. Such requirements are imposed today on substrates both for optical applications (for example, laser gyroscopes) and for microelectronics. Moreover, it is shown that this method allows to reveal and characterize the regular monoatomic steps created at some types of processing on the surfaces of single crystals. We show the possibilities of x-ray reflectometry for characterization of multilayer systems used in microelectronics, as well as for the analysis of layers on the surface of liquids, which sometimes can be considered as models of biological membranes. In all these cases, we are talking about layers with a thickness from fractions to several tens of nanometers.
However, you often have to examine objects where there is no any order. Then one can apply X-ray microtomography. The report presents the principles of x-ray microtomography, including physical ideas used in the design of microtomographs and three-dimensional reconstruction of two-dimensional experimental data. A number of examples show the effectiveness of the use of x-ray microtomography in biological and medical research, as well as in industrial applications. We present possibilities of the method of topotomography to identify spatial locations of defects in crystals. It is shown that today in laboratory conditions it is possible to achieve micron resolution.
For a number of applications, such resolution is not sufficient. This happens when we want to investigate the structure of protein molecules and their complexes, viral particles, the structure of polymers, etc.. The report presents some examples of such studies.
This work was supported by the Federal Agency of Scientific Organizations (Agreement No 007-ГЗ/Ч3363/26).
Primary author
Prof.
Victor Asadchikov
(FSRC "Crystallography and photonics" RAS)
