Silicon carbide defects

The treatment assumes that the point defects do not interact with each other. This is not a very good assumption because point defect interactions are important, and it is possible to take such interactions into account in more general formulas. For example, high-purity silicon carbide, SiC, appears to have important populations of carbon and silicon vacancies, and Vsj, which are equivalent to Schottky defects, together with a large population of divacancy pairs. 

Different supports are used, (see Section 10.6.4) with different geometry (discs or tubes), thickness, porosity, tortuosity, composition (alumina, stainless steel, silicon carbide, mullite, zirconia, titania, etc.), and symmetry or asymmetry in its stmcture. Tubular supports are preferable compared to flat supports because they are easier to scale-up (implemented as multichannel modules). However, in laboratory-scale synthesis, it is usually found that making good quality zeolite membranes on a tubular support is more difficult than on a porous plate. One obvious reason is the fact that the area is usually smaller in flat supports, which decreases the likelihood of defects. In Figure 10.1, two commercial tubular supports, one made of a-alumina (left side) and the other of stainless steel (right side) used in zeolite membrane synthesis, are shown. Both ends of the a-alumina support are glazed and both ends of the stainless steel support are welded with nonporous stainless steel to assure a correct sealing in the membrane module and prevent gas bypass. 

A.I. Girka, E.N. Mokhov, Vacancy defects in silicon carbide, Phys. Solid State, 37, 3374-3381 (1995). 

The successful fabrication of SiC based devices cannot be realized without reliable etching and cleaning processes for this material. The purpose of this Chapter is to review the developments and methods of etching silicon carbide for device applications. The term etching is used to describe the processes by which SiC material can be removed. It also includes chemical machining of a semiconductor as part of the fabrication process, as well as defect delineation. 

Can we grow large area defect-free boules of silicon carbide 3C, 4H and/or 6H ... 

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