**2.2. Epitaxy growth**

Epitaxy refers to the growth of a single crystal film on top of a single crystal substrate. The deposited film is denoted as an epitaxial film or epitaxial layer. The growth is called homoepitaxy if the film and the substrate are the same material, and it is called heteroepitaxy if they are different materials. Epitaxial relationship is determined as: (*HKL*) || (*hkl*); [*UVW*] || [*uvw*], where (*hkl*) and (*HKL*) are the Miller indices of the overgrowth plane and substrate at the common interface. The corresponding parallel directions in the overgrowth and substrate planes, denoted by [*wuw*] and [*UVW*], respectively, must also be specified.
