Papers by Author: Tadeusz Łukasiewicz

Abstract: In this work results of nitrogen doping in the amount of 0 vol.%, 3 vol.% and 10 vol.% on the growth of the 4H polytype on the 6H-SiC seed are presented. SiC crystals grown by PVT method on the (000-1) C-face of 6H seeds using the open seed backside design have been investigated. Structural and electrical properties of the crystals were studied by different experimental methods.

Abstract: The high quality Sr0.61Ba0.39Nb2O6 (SBN61) single crystals without any striations were obtained by Czochralski pulling method. The temperature dependence of the lattice parameters of the investigated crystals was studied using a precision X-ray Bond's method. The angular precision of the goniometer 1 arcsine and metric value of Cu K1 (λ = 1.54059292Å) allowed to obtain high precision and accuracy of lattice parameter measurements. The received results allowed to determine the Curie temperature and character of the phase transition in this material. The lattice parameter a monotonically increases and shows hardly visible inflection point at TC when increasing the temperature. The temperature dependence of the lattice parameter c displays quite distinct temperature behaviour. Contrastingly, it decreases with increasing the temperature experiencing an evident anomaly in the vicinity of the structural phase transition point. Obtained value of the ferroelectric phase transition point is TC = 346 ± 3K.

Abstract: In this work we present the growth of 4H-SiC crystals (2 inch in diameter) on the 8° off- axis C-face 6H-SiC seeds, inclined toward [11-20] direction. The growth of crystals by physical vapour transport method (PVT) was realized with the open seed backside in the experimental setup with graphite resistive heater. Some of the crystals were doped with cerium in the purpose of the 4H polytype growth stabilization. For Ce-doped crystals the seed backside carbonization process was decreased in comparison with such effect observed in the undoped SiC crystals.

Abstract: 4H-SiC single crystals grown by the seeded physical vapour transport method have been investigated. These crystals were grown on 6H-SiC seeds. The influence of the seed temperature, form and granulation of SiC source materials on the stability and efficiency of the 4H polytype growth have been investigated. A new way of the seed mounting - with an open backside - has been used. Crystals obtained were free of structural defects in the form of hexagonal voids. The crystalline structure of SiC crystals was investigated by EBSD (Electron Backscatter Diffraction) and X-Ray diffraction methods. Moreover, defects in crystals and wafers cut from these crystals were examined by optical, scanning electron and atomic force microscopy combined with KOH etching.

Abstract: Single crystals of composition Sr0.61Ba0.39Nb2O6 (space group P4bm) were prepared using the Czochralski method. The Bond's method of the precise lattice parameter measurements was used to study structure of SBN 61 at room temperature. In this way lattice parameters a = b = 12.45676 ± 6*10-5Å and c = 3.93541 ± 5*10-5Å were determined.