Popovych D. Physico-chemical properties of low-dimensional laser-formed oxide and nitride structures.

In the dissertation for the first time, holistic and generalized results of establishment of laws and mechanism of formation of thin films and nanopowder as well as structures based on them using laser in chemically active environment were obtained, peculiarities of their structure, mechanical and physico-chemical properties were investigated. Mathematical modeling of condensation processes and growth of GaN thin films was carried out, dependence of the speed of the growth of layers on the change of temperature of condensation and on flux densities of condensed atoms was established. Within the density functional theory research of energy spectrum of small clusters (ZnO)n (n=2-12) was performed and conditions of their energetic stability were determined. New methods to control component and energy states in the laser plume were developed and implemented, which determine controlled growth, high purity, crystal perfection and given chemical composition of the material. Monocrystalline epitaxial thin films of oxide ZnO, ZnGa2O4, K2Ga2O4, Zn2SiO4, Zn0,4Gd1.6O3, Y2O3:Eu, ZrO2 and nitride GaN, GaN:Zn, GaN:Mn, GaN:Cr, AlN, AlN:Mn, MgSiN2 materials with bright luminescence in the blue, green and red areas of the spectrum were created. Qualitative and quantitative characteristics of disperse and chemical compositions and structural parameters of the synthesized nanopowder ZnO and TiO2 materials in dependence on technological mode and geometry of laser ablation were obtained. Luminescent method of gas detection and identification in the analyzed environment was offered. Influence of molecular gases O2, H2, N2, CO і СО2 adsorption on the change the photoluminescence of nanopowder ZnO і TiO2 was studied. Nanoscalable doped layered single crystals GaSe, InSe with embedded Mn, Ni and Cr were obtained and realization of giant magnetoresistive effect in them was proved.