The atomic force microscopy-based local oxidation (AFM-LO) of silicon carbide (SiC) is extremely difficult in general, mainly due to their physical hardness and chemical inactivity. Herein, we report the strongly enhanced AFM-LO of 4H-SiC at room temperature without the heating, chemicals or photoillumination. It is demonstrated that the increased tip loading force (∼>100 nN) on the highly doped SiC can produce a high enough electric field (∼8×106 V/cm) under the cathode tip for transporting oxyanions, thereby leading to direct oxide growth on 4H-SiC. The doping concentration and electric field profile of the tip-SiC sample structures were further examined by two-dimensional numerical simulations.

We present experimental results with regard to the evaluation of growth-induced polytype domains in 6H-SiC crystals grown by sublimation method and these domains are characterized by using the polarized optical microscopy and micro-Raman spectroscopy. The polytype domains of reverse triangular are generated by local variation of temperature along cdirection and spread-wing shapes normally occurred forming micropipes in many cases. These polytype domains may be generated due to the local variation of supersaturation and/or temperature at central position during crystal growth. In this work, we try to elucidate the origin and mechanism responsible for growth-induced polytype domains.

The variation of nitrogen doping concentration was systematically investigated with respect to the amount of silicon powder added to the SiC powder for growing n-type 6H-SiC single crystal by the sublimation method. To change intentionally the Si content in the SiC powder, 0wt% to 2wt% of a silicon powder was added to first-thermal treated SiC powder and the mixed powder was treated again at 1800oC for 3 hours to eliminate excess free-metallic silicon. Nitrogen doped 6H-SiC single crystals were grown by using 2nd-thermal treatment SiC powder at fixed N2/(Ar + N2) (3%). The nitrogen doping concentration of 6H-SiC crystals increased with increasing Si content in the SiC powder. In this work, we could identify that the additional silicon powder in SiC powder plays a role in the enhancement of nitrogen doping in 6H-SiC crystals grown by the sublimation method.

We present experimental results regarding to the evaluation of growth-induced defects in 6H and 4H SiC crystals grown by sublimation method, and these defects are characterized by using micro-Raman spectroscopy. From Raman results, we could reveal the stacking disorders related to strain which occurs along the boundary position of planar defects and micropipes in 6H SiC crystals. Also, we found the 15R was generated due to the change of stacking sequence from 4H to 15R during crystal growth because the 15R formation area is adjacent to 4H, considering the relation between formation probability and temperature.

We examined the formation of poly-crystals and polytypes under the point of view applying various powder phases. 6H-SiC single crystal was easily grown by using the green (α-SiC) powder, while the poly-crystals were generated when β-SiC powder was utilized. The method of mixed β-SiC and carbon powder and of graphite pipe inserted in β-SiC powder were applied to overcome the generation of poly-crystals, respectively. It was confirmed that the occurrence of poly-crystals in 6H-SiC crystal was successfully suppressed by C-rich environment.