Papers by Author: J. Gyulai

Abstract: A brief historical overview of one of Hungary's space projects on Soviet spacecrafts, the so-called "Eötvös" Project on semiconductor crystal growth, is given. Three experiments were proposed and performed: i) epitaxial growth of GaAs under flux, ii) seedless growth of GaSb, and as a control, iii) seeded growth of an InSb crystal. Because of thermal control problems of the furnace, only the growth of a structurally perfect GaSb bicrystal was a successful novelty. Results of structural and electrical analyses are briefly summarized. Finally, a list of related publications is given.

Abstract: This study focused on the effect of ion implantation on the mechanical properties of silicon nitride based ceramics. The examined materials contained 4% Al2O3, 6% Y2O3 and, in some cases, graphite or black carbon additives. Fully densified bodies were manufactured by two-step hot isostatic pressing, in other experiments pressureless sintering gave porous ceramics. Nitrogen or carbon ions with 190 keV or 350 keV were implanted, a part of samples obtained laser treatments for comparison. Measurements of elastic modulus, four point and three point bending strength were carried out at room temperature on sintered samples, partially sintered samples and sintered and oxidised samples. Carbon or nitrogen implantation influenced the strength of partially sintered samples only if the density was over 80%. Both the implantation of carbon or nitrogen ions and the laser treatment affected the bend strength of sintered samples, enlarging the power introduced its value first increased than decreased. Implantation slightly decreased the strength of samples oxidised at 1400 °C. Comparison of different mechanical characteristics may support a better understanding of phenomena during ion beam implantation or laser irradiation.

Abstract: 500 keV nitrogen implantations at different tilt angles (0o, 0.5o, 1.2o, 1.6o, 4o) with respect to the c-axis of 6H-SiC were carried out. Radiation damage distributions have been investigated by Backscattering Spectrometry combined with channeling technique (BS/C) using 3550 keV 4He+ ion beam. A comparative simultaneous evaluation of the damage depth distributions in the Si and C sublattices of 6H-SiC led to a correction factor of 0.8 in the electronic stopping power of 4He+ ions along <0001> channel. Full-cascade Crystal-TRIM simulations with the same set of damage accumulation model parameters could reconstruct the measured shapes and heights of damage distributions for all implantation tilt angles. Secondary defect generation effects in addition to the primary point defect accumulation were assumed in the analysis.