Silicon carbide

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Polycrystalline SiC for mechanical applications.
Single crystalline SiC for electronic purposes. Image taken before cutting into thin wafers.

Silicon carbide (SiC) is a mineral which occurs extremely rarely in nature. When it does it is referred to as moissanite. It is probably most commonly known for its use as an abrasive due to the extreme hardness of the material, which is only exceeded by the hardness of diamond.

However, SiC is also being researched extensively for applications as a semiconductor for applications requiring high power, high frequency or a large degree of chemical inertness. It is employed in high power Schottky diodes.

SiC can exist in an infinite variety of crystal structures (all composed of 50% Si and 50% C atoms), thus exihibiting polytypism. Each SiC polytype is unique in the ordering of double layers of Si and C atoms, the simples being the 2H-SiC polytype so-called because of its repeating 2 double layers and hexagonal structure. The most studied polytypes for electronic use is 3C-SiC (cubic), 4H-SiC and 6H-SiC.