Papers by Author: Juan Li

Abstract: the multimedia technology in teaching in the classroom, it can help students to break through the difficulty, quickly and accurately model, improve the efficiency of the whole teaching and promote the teaching reform, is the basic concepts and the current as a preliminary discussion on some problems in practical application.

Abstract: 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.

Abstract: 6H-SiC ingots were grown with different growth interfaces at different rates via the sublimation method. A model for the step flow growth mechanism is proposed to interpret the occurrence of 15R-SiC inclusions in the 6H-SiC single crystal. The results show that the 15R-SiC occurs more easily on the convex and the concave interface than on the slight convex interface and 15R-SiC inclusion also occurs when the growth rate of 6H-SiC exceeds the critical rate of 300 %m/h with the slight convex interface at the seed temperature 2250°C.