Papers by Author: Bernard Ferrand

Abstract: We report the effect of changing the growth conditions in the case of bulk 3C-SiC crystals grown by the Travelling Zone Method when the seed is placed on the top graphite rod. First, we investigated the effect of changing the temperature gradient and the cooling ramp. Next we studied the effect of changing the seed polytype and misorientation. Every time, working in the 1700 °C temperature range, the grown polytype was 3C. From X-ray analysis we evidenced a better hetero-epitaxial relationship between the seed and layer when a low misorientation angle was used. Better quality and homogeneity were obtained on the first 500 .m of the layer and, beyond this thickness, micro-Raman measurements show that the effect of solvent (Si) incorporation is not yet fully under control.

Abstract: The paper presents two cerium doped lutetium silicate crystals: pyrosilicate Ce:Lu2Si2O7 (LPS) and Ce: Lu2(1-x)Y2xSiO5 (LYSO). These two crystals exhibit the expected requirements for gamma detection: high density and high atomic number, high scintillation light yield, good energy resolution and fast response. LPS and LYSO crystals doped with cerium were grown by the Czochralski process. The crystal growth parameters were studied and optimized. Development of scintillators requires good understanding of the scintillation process. The location within the forbidden band gap of the localized lanthanide energy levels is analyzed by time resolved spectroscopy and thermoluminescence studies.

Abstract: Cubic-silicon carbide crystals have been grown from solution by using the traveling-zone method. In this technique a molten silicon zone heated by induction coils is held between two rods of polycrystalline silicon carbide. Due to the growth set-up and boundary conditions, different mass transfer mechanisms are operative : diffusion, buoyancy, Marangoni convection and forced convection. The growth experiments have been performed on various seed crystals. Cubic SiC crystals were grown with a [111] habit on the [0001] silicon faces of 4H SiC seeds. The polytype 3C-SiC was identified by Transmission Electron Microscopy. Micro Raman spectroscopy and photoluminescence analyses showed good crystalline quality with few 6H inclusions.