SiC Cage Like Based Materials

Abstract

SiC is a compound of silicon and carbon with a chemical formula SiC. Silicon carbide(SiC) as a material is the most promising for applications in which high-temperature, high-power, and high-frequency devices, catalyst support, high irradiation environments are needed. Naturally occurring SiC is found only in poor quantities that explains the considerable effort made in the industrial SiC engineering. At a first glad, silicon and carbide are close but a careful inspection reveals different properties leading to brothers at odds behavior. In well ordered stoichiometric compounds SiC adopts a tetrahedral bonding like observed in common semiconductors (zincblende and wurtzite are the most populars). The difference of electronegativities induces a ionicity which is not enough to promote NaCl or CsCl structures but enough to induce multipolar effects. These multipolar effects are responsible to the huge number of polytypes. This polytypism has numerous applications including quantum confinement effects and graphene engineering. In this chapter, special emphasis has been placed on the non stoichiometric compounds. Silicon architectures are based from sp3 or more dense packing while carbon architectures cover a large spread of hybridization from sp to sp3, the sp2 graphite-like being the stable structure in standard conditions. Whenwe gather silicon and carbon together one of the basic issue is: what is the winner? When silicon and carbon have the same concentration (called stoichiometric compound), the answer is trivial: "the sp3" lattice since both the elements share this hybridization in bulk phase. In rich silicon phases, the sp3 hybridization is also a natural way. However, a mystery remains when rich carbon compounds are synthesized. Silicon sp2 lattice is definitively unstable while carbon adopts this structure. One of the solution is the cage-like structure (the fullerenes belongs to this family) where the hybridization is intermediate between sp2 and sp3. Other exotic structures like buckydiamonds are also possible. Special architectures can be built from the elemental SiC cage-like bricks, most of them are not yet synthesized, few are experimentally reported in low quantity. However, these structures are promising as long the electronic structure is quite different from standard phase and offer new areas of research in fuel cells (catalysis and gas storage), superconductivity, thermoelectric, optical and electronic devices. . .Moreover, the cage like structure permits endohedrally doping opening the way of heavily doped semiconductors strain free. Assembling elemental bricks lead to zeolite-like structures. We review the properties of some of these structures and their potential applications. 2