A single Crystal is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries. The absence of the defects associated with grain boundaries can give single crystals unique properties, particularly optical, electrical, and mechanical. These properties, in addition to making them precious in some gems, are industrially used in technological applications, specially in optics and electronics.

Single Crystal substrates has a unique combination of physical, chemical and optical properties allowing it to withstand high temperatures, high pressures, thermal stock and water or soil erosion. It is chemically inert with a low friction coefficient and excellent electrical, optical and dielectric characteristics.

Single crystal substrateshas been widely used as substrate material for the deposition of high quality oxide thin films, including semiconducting, superconducting, dielectric, ferroelectric, and ferromagnetic oxides. The quality of the oxide films is strongly correlated to the quality of the substrate.

The anistropicproperties of crystals depends on the orientation of crystals and lead to a wide range of applications in research and development. Crystal substrates has hexagonal/rhombohedral structure. For epitaxial growth of films, different orientations will offer a range of lattice constants to match the epi material.

Single crystal substrates are of three types: C-plane, A-plane, R-plane.

C-plane substrates are used to grow III-V and II-VI compounds such as GaN for blue LED and laser diodes. A-plane substrate provide a uniform dielectric constant and high insulation for hybrid microelectronics applications. R-plane substrates are used for the hetero-epitaxial deposition of silicon for microelectronic IC applications.