Papers by Author: N. Korsunska

Abstract: RF magnetron sputtering of two separate silicon and oxide (SiO₂ or Al₂O₃) targets in pure argon plasma was used for deposition of Si_x(SiO₂)_1-x and Si_x(Al₂O₃)_1-x films with x=0.15-0.7 on long fused quarts substrate. The effect of post-fabrication treatments on structural and light emitting properties of the films with different x values was investigated by means of Raman scattering, electron paramagnetic resonance and X-ray diffraction as well as by photoluminescence (PL) methods. The formation of amorphous Si clusters upon deposition process was found for the both types of films. The annealing treatment at 1150°C during 30 min results in formation of Si nanocrystallites (Si-ncs). The latter were found to be larger in Si_x(Al₂O₃)_1-x films than that in Si_x(SiO₂)_1-x counterparts with the same x values and are under tensile stresses. The investigation of photoluminescence properties of annealed films of both types revealed the appearance of visible-near infrared light emission. The Si_x(SiO₂)_1-x films demonstrated one broad PL band which peak position shifts gradually to from 1.4 eV to 1.8 eV with the x decrease. Contrary to this, for the Si_x(Al₂O₃)_1-x films two overlapped PL bands were observed in the 1.4-2.4 eV spectral range with peak positions at ~2.1 eV and ~1.7 eV accompanied by near-infrared tail. Comparative analysis of PL spectra of both types samples showed that the main contribution to PL spectra of Si_x(SiO₂)_1-x films is given by exciton recombination in the Si-ncs whereas PL emission of Si_x(Al₂O₃)_1-x films is caused mainly by carrier recombination either via defects in matrix or via electron states at the Si-ncs/matrix interface.

Abstract: The properties of SiOx layer prepared by magnetron sputtering is studied by photoluminescence Auger and SIMS methods. The depth distribution of emission characteristics and chemical composition is obtained. It is shown that as-sputtered SiOx layers are non-emitted and characterized by homogeneous enough chemical composition. High-temperature annealing in nitrogen atmosphere stimulates not only the Si nanocrystal formation but also the redistribution of silicon and the appearance of Si depleted region near layer-substrate interface. The last process is found to be dependent on excess Si content. It is found that decrease of silicon content in the depth of annealed layers is followed by the decrease of particle sizes that is proved by the blue shift of photoluminescence maximum. The possible reasons of the appearance of Si depleted region are discussed.

Abstract: The properties of SiOx layer prepared by magnetron sputtering is studied by photoluminescence Auger and SIMS methods. The depth distribution of emission characteristics and chemical composition is obtained. It is shown that as-sputtered SiOx layers are non-emitted and characterized by homogeneous enough chemical composition. High-temperature annealing in nitrogen atmosphere stimulates not only the Si nanocrystal formation but also the redistribution of silicon and the appearance of Si depleted region near layer-substrate interface. The last process is found to be dependent on excess Si content. It is found that decrease of silicon content in the depth of annealed layers is followed by the decrease of particle sizes that is proved by the blue shift of photoluminescence maximum. The possible reasons of the appearance of Si depleted region are discussed.

Abstract: The effect of preparation conditions and annealing treatment on Si-rich-SiOx layers was investigated. It was observed that oxygen plays important role in the creation of light-emitting centres. It was found that the emission in the green-orange spectral range is connected with silicon oxide defects which contain dangling bonds. At the same time PL band in the infrared spectral range is caused by recombination of carriers in amorphous silicon or nanocrystalline one. It is shown that modification of defect content under various treatments gives the possibility to control the emission properties of the layers.

Abstract: The aging process of silicon nanostructures obtained by magnetron sputtering and electrochemical etching is investigated by photoluminescence and Raman scattering methods. It is shown that oxidation of silicon crystallites takes place in both types of structures and results in appearance of additional emission bands. However the degree of oxidation in etched structures exceeds significantly this value for sputtered samples. It is found that the intensity and spectral position of the emission band caused by exciton recombination in Si crystallites do not change practically during aging in sputtered structures in contrast to etched ones. It is shown that the oxidation of silicon amorphous phase occur during aging in sputtered structures.

Abstract: In this chapter we present the results of the photoluminescent and optical investigations of the influence of cation vacancy-related defects on CdSe/ZnSe quantum dot organization. Selfassembling growth was achieved under molecular beam epitaxy with subsequent annealing step. Number of cation vacancies was controlled by the intensity of the emission band connected with complex that includes cation vacancy and shallow donor. For the first time it is shown that increase of number of cation vacancy related defects results in the reduction of potential fluctuations in the QD layer. In this case a relatively uniform dense array of QDs with shallow localization potential is organized. It is proposed that generation of cation vacancies during the growth suppresses both Cd segregation and Cd surface diffusion as well as facilitates Cd/Zn interdiffusion. Interdiffusion process is proved by the changes in the photoluminescence and optical reflection spectra of ZnSe layers. It is showned that Cd/Zn interdiffusion can play an important role in CdSe/ZnSe intermixing during the QD formation at least under such growth conditions which can stimulate generation of cation vacancies.