Polarization microscopy was a suitable tool for studying strain in appropriately cut SiC single crystals. The outline shape examined by electron microscopy and the induced interference pattern observed by polarization microscopy were both used to study the variation and character of macro-defects present in SiC wafers. While voids were usually in a relaxed state, hollow-core dislocations were characterized by large interference halos up to ∼100 µm in diameter. Conoscopy, i.e. evaluation of the interference pattern created by inserting an Amici Bertrand lens, was used to examine these optical phenomena in more detail and gain additional knowledge on the inclination of wafers cut towards the c-axis. The discrepancy between the simulated and observed interference patterns for (00•1)-SiC strongly indicated that pipes were not pure screw dislocations, as commonly thought, but have an edge component.

Scanning Electron and Polarization Microscopy Study of the Variability and Character of Hollow Macro-Defects in Silicon Carbide Wafers. V.Presser, A.Loges, K.G.Nickel: Philosophical Magazine, 2008, 88[11], 1639-57