Handbook of Silicon Based MEMS Materials and Technologies

1.1.1. Crystallography of Silicon

Silicon crystallizes into a diamond cubic crystal structure (Figure 1.1) in which the atoms are covalently bonded. Other elements, like germanium, in periodic table group IV typically have the same structure. The unit cell contains 8 atoms, and the atoms follow a face centered cubic (fcc) Bravais lattice. In each fcc lattice point there are 2 atoms (motif): one in the lattice point and the second displaced by ¼ of the unit cell length towards the [111] direction. The unit cell length at room temperature is 0.5431 nm. Actually, this value is one of the most precisely known among elements, since silicon crystal can be grown almost perfectly, and the lattice parameter can be measured precisely according to Martin ...