Eunjin Jung

Synthesis of beta-SiC powder from alkoxide precursor and study of its sintering behaviour

Abstract Abstract In this study, β-SiC powder was prepared using a pyrolysed spherical precursor derived from the hydrolysis mixture of phenyltrimethoxysilane and tetraethyl orthosilicate. Before the pyrolysed experiment, an alkoxide precursor was characterised using 29Si solid nuclear magnetic resonance, Fourier transform infrared spectroscopy and thermogravimetric analysis. The alkoxide precursor was heated at 1800°C for 4 h under an Ar atmosphere. To examine the pyrolysed residue after heat treatment, the sample was collected and analysed with X-ray diffraction. The X-ray diffraction results for the sample show diffraction peaks at ∼35, 60 and 73°, which correspond to the β-SiC phase. According to the results of chemical analysis, the SiC content of the powder that was prepared at 1800°C was determined to be 99·4%. The sintering behaviour of the prepared β-SiC powder was examined using B4C and C as sintering additives in the temperature range of 1900–2200°C.

Mapping analysis of single crystal SiC polytypes grown from purified β-SiC powder

The most important consideration when growing single crystal silicon carbide by the physical vapor transport method is to minimize defects. To minimize defects caused by temperature gradient, we used β phase SiC powder, which has a low sublimation temperature, and purified the β phase SiC powder to improve the purity of single crystal SiC. Furthermore, we performed thermodynamic computational simulations based on compositions of purified and non-purified β-SiC powders to study the impact of metallic impurities within SiC powder on the composition of single crystal SiC. We grew SiC at temperatures about 200 °C lower than the previous growth temperature using purified β-SiC powder and mapped the phase change behavior of SiC according to different growth temperatures. Moreover, we compared and analyzed the characteristics of SiC polytype formation and crystallinity according to growth temperature. We compared the distribution of defects and dislocations of single crystal 4H SiC grown from purified and non-purified β-SiC powder to study the impact of source purification on defect generation. We also investigated the effect of metallic impurities on the formation of defects and dislocations through content analysis of metallic impurities.

Purification and particle size control of β-SiC powder using thermocycling process

Abstract Recently, SiC single crystal growth has been of interest for the development of an alternative semiconducting material. The aim of this study was to purify and grow β-SiC particles for use as a single crystal source. First, a β-SiC powder with a particle size of about 10 μm and a purity of 99·5% was prepared from a phenyl-containing silica sol. Then, three different of heat treatment process were applied to grow the β-SiC particles and evaluate the effects of heat-treatment time and temperature. After three thermocycling processes carried out from 1850 to 2000°C in 1 h, the β-SiC particles had diameters over 100 μm because of a vaporisation–recrystallisation process that accelerated the β-SiC particle growth. Moreover, the thermocycling process improved the purity of β-SiC by eliminating metallic impurities.