Dr. P. Lucas U of A MSE 110 Band StructuresSUMMARY FROM LAST CLASS•There are three types of band structures associated with each types of primary bonding which determine the properties of electrical conductivity of solid materials.•Metals are conductors and have either a partially filled s, p, or d band or an overlapping full and empty bands which generate an overall partially filled energy band.•Ionic solids are insulators. They are composed of atoms of very different electronegativityhaving orbitalsof very different energy which generate two separate bands. An empty conduction bandand a full valence bandseparated by a large band gap.•Semiconductors are tetrahedrallyconnected covalent solids. They are formed of a network of sp3 hybrid orbitalsgenerating a full bonding valence band and a empty antibondingconduction band separated by a small band gap (<4eV) that some electrons can cross.•Binary and ternary semiconductor have an average of four electrons per atom that can form four covalent bonds each.•Visible light is not sufficiently energetic to excite electrons across the gap of insulators which appear transparent, but can excite electrons across the bandgapof semiconductors which appear opaque.•The transparency cut-off wavelength of a material is thengcEhc=λ
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