Semiconductor detectors utilise the semiconducting element germanium. Armchair nanoribbons are metallic or semiconducting and present spin polarized edges. Some materials, when rapidly cooled to a glassy amorphous state, have semiconducting properties. Iodine is also known in a semiconducting amorphous form. Dichlorosilane is used as a starting material for semiconducting silicon layers found in microelectronics. Partially filled variants can be synthesized as semiconducting or even insulating. This prevented electricity from reliably penetrating the surface to reach the semiconducting silicon layer. This is the case for both semiconducting and superconducting materials at low temperature. They are always dark diamagnetic solids, insoluble in all solvents, and exhibiting semiconducting properties. Avalanche breakdown is a phenomenon that can occur in both insulating and semiconducting materials. They exhibit metallic lustre, semiconducting properties and bonding or valence bands with delocalized character. They may be synthesized from metals or semiconducting materials. Avalanche breakdown occurs in semiconducting CNT and joule breakdown in metallic CNT. An alternative to separation is development of a selective growth of semiconducting or metallic CNTs. Uranium dioxide is a black semiconducting solid.