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Physical and technical principles of creating controlled nano- and microstructures on the solid surfaces

Work number - P 12 AWARDED

Presented National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”

Dr.Sci. in physics and mathematics Voitenko A.I., Dr.Sci. in physics and mathematics Gabovich A.M., Dr.Sci. in physics and mathematics Gorshkov V.M., Ph.D. in physics and mathematics Korotash I.V., Dr.Sci. in engineering Kuzmichev A.I., Dr.Sci. in physics and mathematics Rudenko E.M., Ph.D. in physics and mathematics Semeniuk V.F., and Semeniuk N.I.

This scientific work is a result of the long-term studies by the participants in the domains of plasma physics, condensed matter, and interaction of ionic fluxes generated by a plasma medium with metal, semiconducting, and dielectric targets. In the course of the purposeful theoretical and experimental research, the results of which formed a holistic concept and were included into the presented work, the elementary electronic and atomic-molecular processes, as well as collective phenomena inherent to multi-component systems, were studied. During the work, a number of operative installations were created, which are capable of sputtering targets made of metals, semiconductors, insulators, and polymers owing to the interaction of ultra-high-density ion fluxes with the target surface. Magnetron and helicon discharges can be used as effective plasma ion sources. The created equipment is being intensively used nowadays for scientific and industrial purposes. The level of research and developments meets the modern needs of ion-plasma surface engineering in such areas as submicronic electronics, high-temperature superconductivity, carbon nanostructures, precision friction pairs and functional coatings, black silicon for photovoltaics, and silicon-based composite anodes for lithium-ion batteries with enhanced parameters. A new collective (“trampoline”) threshold mechanism of target sputtering was discovered and researched for the first time. This mechanism is realized due to the concentration of the ion flux energy in the near-surface layers of solids, which is a revolutionary step in modern ion-plasma surface engineering. It was shown that the trampoline modification of the substrate surface consists in the formation of a two-level hierarchical structure that promotes strong adhesion between different materials. Superconducting structures created by magnetron sputtering and tunnel effects in superconducting transitions were studied in detail taking into account the nano-scale restructuring of the electronic spectrum occurring due to the formation of charge density waves (CDWs). Tunnel spectra for the so-called break junctions and thin films obtained by magnetron sputtering were studied both experimentally and theoretically. The hump-dip-coherent peak structures in the current-voltage characteristics, which clearly demonstrate the coexistence of CDWs and superconductivity (this phenomenon was predicted by us earlier) were studied at the qualitative and quantitative levels. The cases of coherent and incoherent tunneling were considered.

An important fragment of the work is devoted to the theoretical study of the kinetics of elementary crystallization processes and the formation of nanoclusters and nanopillars. It substantially complements the scope of elementary processes governing the behavior of the nonequilibrium interface between the plasma and the solid that was studied experimentally and explains them. The powerful Monte Carlo method was applied, which allowed the consideration of real, very difficult problems in the many-particle physics. Using a theoretical "microscope", we analyzed elementary processes that form a surface in the course of sputtering and crystallization. Since the particles interacting near the surface are charged or have a permanent electric dipole moment, there arises a necessity in a theory describing Coulomb interaction in two- or three-layer systems. Such a theory was developed in the framework of the presented work. It describes the interaction of particles with a surface or surfaces (image forces), which depends of the screening properties of the media where the particles are located. In particular, it is important for the study of exciton properties in layered structures, including films sputtered using the experimental methods that were applied in this work. Hence, Coulomb interaction, which plays a decisive role in physics of plasma sources and ionic scattering of targets, is the main governing factor here.

The work satisfies the experimental and theoretical criteria adopted in world science. All published results are new, important, and were verified both in practice and at international forums. Some pieces of the work were carried out in co-authorship with scientists from the US, Poland, Japan, South Korea, Germany, Russia, and Slovakia. Results important for applications are covered by 56 patents, including the foreign ones. The results of fundamental theoretical studies were published in the leading English-language journals. The results obtained were systematically lectured at various faculties of the Igor Sikorsky National Technical University of Ukraine as the teaching material of special courses.

Number of publications: 8 monographs, 19 chapters in collective monographs and conference proceedings, 180 journal articles (67 in English-language Q1 journals and 38 in English-language Q2 journals). According to the scientific databases, the total number of citations to those publications and the corresponding h-index of publications are, respectively, 1746/22 for Web of Science, 1958/24 for Scopus, and 2468/26 for Google Scholar. Three doctoral and eleven Ph.D. theses were defended on the given subject.