The origin of the internal stresses around micro-pipes in hexagonal-type single crystals was investigated by using a strain model. A model made from acrylate resin demonstrated perfectly the strain distribution around micro-pipes. The strain distribution was confirmed by interference patterns which were observed by using photo-elastic measurements under crossed-polar conditions. It was proposed that micro-pipes were formed by stress relaxation at the centre of screw dislocations. However, the strain model demonstrated that the stress origin around micro-pipes involved edge dislocations which were located at the centre of micro-pipes in the (00▪1) basal plane. Micro-pipe formation was suggested to occur due to mixed screw and edge dislocations.

Origin of the Internal Stress Around the Micropipes of 6H-SiC Single Crystals. T.Kato, H.Ohsato, T.Okuda: Materials Science Forum, 2000, 338-342, 449-52