Bulk 4H-SiC crystals were grown on 4° off-axis seeds by the physical vapor transport technique. Two completely different surface morphologies of as-grown crystals were observed by laser scanning confocal microscopy. The formation mechanisms of the different surface morphologies are proposed and discussed. We found that the facet formation and migration on the 4° off-axis seeds largely depended on the profile evolution of the temperature field in the growth cell over a long-term growth run. At the interface between the two growth regimes, some grown-in defects, including micropipes, dislocations and polytype inclusions, were frequently observed by polarizing optical microscopy and chemical etching. The stress induced by step coalescence could be responsible for the formation of these grown-in defects.
Wafer-scale graphene on SiC with uniform structural features was grown on semi-insulating 4 inch on-axis 4H-SiC (0001) face. Growth was carried out in a conventional physical vapor transport (PVT) growth system. Atmospheric pressure graphitization and a “face-down” orientation were account for the high uniformity of graphene. Atomic force microscopy, electrostatic force microscopy and Raman spectroscopy were used to confirm the uniformity of surface morphology and layer number. Electrical properties were also characterized by Hall measurements on 15×15mm2 samples sawed from the wafer. An average Hall mobility of about 2000cm2/Vs was obtained.
4H-SiC single crystal with a diameter of 1.5’’ has been grown by the seed sublimation method. Regions of mixed polytypes are assessed by high resolution X-ray diffractometry with the asymmetrical diffraction geometry. Multiple reflections are observed from the rocking curve measurements of a longitudinal cut 4H-SiC slice. Those reflections are indexed to be 2131 and 2131 of 4H-SiC, 2130 , 2131 , 2131 , 2132 and 2132 of 6H-SiC, 2131 , 2132 , 2134 , 2135 and 2137 of 15R-SiC respectively based on the lattice constants of different polytypes in SiC crystal. It is believed that the polytypes can be identified by high resolution X-ray diffractometry.
A new family of membrane phosphoproteins designated as P9, P12, P15, P16, and P20 with corresponding apparent molecular weights of 9K, 12K, 15K, 16K, and 20K was characterized from rat brain by using in vitro exogenous or endogenous phosphorylation and autoradiography. As the phosphorylation was selectively inhibited by the protein kinase C (PKC) inhibitor PKC, 931 or Ca 2~-chelatingreagents and again stimulated by the PKC activator phorbol 12,13-dibutyrate, these proteins are thought to be the natural PKC substrates. Because P12, P15, P16, and P20 were neutral proteins (p1 7.0) and specifically distributed in neuronal membranes, the new family of membrane-associated PKC substrate proteins was referred to as neutrinins. Neutrinins were widely distributed in rat brain, being especially plentiful in the spinal cord, medulla oblongata, cerebellum, and midbrain, relatively scanty in the cerebral cortex, but lacking in cytosbl of brain areas and cell membrane preparations of peripheral tissues. The expression of the developmental changes of neutrinins has been monitored by the in vitro exogenous phosphorylation approach, i.e., adding purified PKC to a deactivated synaptosomal plasma membrane system. Levels of all the neutrinin proteins in rat cerebral cortex, as represented by P12, P15, and P16, showed an ontogenetic increasefrom the early postnatal days to the adult. This appears to be correlated with the commencement of synaptogenesis.
Two SiC crystals were grown using SiC source powder with different level of purity and then the effect of the purity of SiC source materials on the final electrical properties has been systematically observed. Furthermore, the variation of vanadium amount according to the growth direction of vanadium doped semi-insulated SiC single crystals has been investigated. The quality of SiC crystal grown using SiC source powder with higher purity was definitely better than SiC crystal with lower purity. SiC crystals having an average resistivity value of about 1×1010 Ωcm were successfully obtained. In the result of COREMA measurement, the use of high purity SiC powder was revealed to obtain wafers with better uniformity in resistivity value.
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