The most common semiconductor, atomic number 14, energy gap Eg=1. 12 ev-indirect bandgap; crystal structure- diamond, lattice constant 0. 543 nm, atomic concentration 5x1022 atoms/cm, index of refraction 3. 42, density2. 33 g/cm3, dielectric constant 11. 7, intrinsic carrier concentration 1. 02x1010cm-3, mobility of electrons and holes at 300º K: 1450 and 500 cm2/V-s, thermal conductivity 1. 31 W/cmºc,thermal expansion coefficient 2. 6x10-6 ºc-1, melting point 1414ºc; excellent mechanical properties (MEMS applications); single crystal Si can be processed into wafers up to 300mm in diameter.