Dmitruk I. Spectroscopy of elementary excitations in bulk crystals and nanoparticles of direct bandgap semiconductors

Object of investigation - semiconductor crystals of oxides, phosphides, iodides, AIIBVI compounds and their nanostructures. The purpose - the study of the processes of light interaction with excitonic and biexcitonic elementary excitations in semiconductor crystals and nanostructures in wide intensity range. The theoretical methods, numerical models, spectroscopic methods including pico-and femtosecond spectroscopy, electron and scanning-probe high resolution microscopy, mass-spectroscopy, X-ray analysis. The existence of excited states of excitonic molecules is demonstrated for the first time by direct method of giant two-photon absorption. Spectroscopic manifestation of the existence of new mechanism of resonant exchange of excitation energy in inelastic scattering of excitonic molecules is found. Direct measurements of thermalization time of resonantly excited "cold" excitonic molecules in b-ZnP2 are performed for the first time. The lifetime of excitonic molecules in the ground and excited state isdetermined. A new kind of polaritonic phenomena arising from formation of the two-photon-biexciton polaritons have been theoretically and experimentally studied. Collective effects with participation of "ultracold" excitons have been studied in luminescence spectrum of Cu2O crystal under resonant excitation. The possibility of application of size-selective photochemical etching for preparation of semiconductor nanoparticles with desired size has been demonstrated. New type of the binary compound (AIIBVI)n nanoclusters which consist of high symmetry fulleren-like external shell with one or more atoms inside has been found. The most stable clusters are (AIIBVI)33 and (AIIBVI)34. Application domain - the spectroscopy of crystals, nanophoptonics, optoelectronics.