Study On The Growth Process And Gemmological Characteristic Of Silicon Carbide

Synthetic carbon silica is one of the third generation semiconductor materials. Ithas been widely used in electronic products because of its excellent electricalproperties. It also can be used as a gemstone with high luster, dispersion and thermalconductivity properties, which are close to them of diamond. Moreover, the colorlesscrystal is known as the best imitation for diamond.This paper studies the growth process of green and yellow synthetic carbon silica.The temperature and air pressure are between2150~2250℃and5×10~7~1×10~9MParespectively. Temperature gradient should be controlled between30~50℃/cm and ittakes100hours to grow up. The crystal bar is25mm long, and the diameter is55mm.This paper applied X-ray powder diffraction technique for the composition andstructure of crystals. The main composition is6H-SiC, containing a small bit ofgraphite. It was proved to be hexagonal system and cell parameters is a=b=3.08077,c=15.11168. Crystal has high quality, excluding other phase impurities.Si-C telescopic vibration can be found in the sample through the Fourier infraredspectral in the samples which are pure. Meanwhile, reflection spectrum is closelyrelated to the concentration of carriers. The concentration of carriers can be shown asthe minimum values move to direction of high frequency, with the remaining raysbecoming more flat and wide.It can be found that N elements of the shallow benefactor level is the mainreason for green, and V elements of the warp level is not fit for the experimentalresults which needs further research through the ultraviolet-visible absorption spectralresearch.The paper made observation and analysis of crystal defects, including a wrong,curl up and micro tube line with optical microscope and field emission scanningelectron microscopy to study the shape of the micro tubes and its distributioncharacteristics, showing that the diameter of the micro tubes is about1.5micron to15 microns and the pipes are caused by dislocations which may due to the existence of Siimpurities.The synthesis process should be more precise, stable in controling thetemperature change of the growth to make temperature field distribution more even.The raw material, crucible and the carrier need to purify toreduce the impurity.This paper also study the gemological characteristics of green and yellowsynthetic carbon silica. The gem samples present dark green,adamantine luster, withrefractive index of about2.607, absolute hardness of3160N/um2and special gravityof3.24g/cm~3.