Single crystal sapphire has a unique combination of physical, chemical and optical properties allowing it to withstand high temperatures, high pressure, thermal shock, and water or sand erosion. It is chemically inert, with a low friction coefficient, and excellent electrical, optical, and dielectric characteristics. In addition, its radiation resistance makes it an excellent material for use in optical windows for space applications
Sapphire has a hexagonal/rhombohedral structure and a number of properties are dependant on the orientation of the crystal. For epitaxial growth of films, different orientations will offer a range of lattice constants to match the epi material.
C-plane sapphire substrates are used to grow III-V and II-VI compounds such as GaN for blue LED and laser diodes. In addition, it is useful for infrared detector applications.
A-plane sapphire substrates provide a uniform dielectric constant and high insulation for hybrid microelectronic applications. High Tc superconductors can be grown with a-plane Sapphire substrates.
R-plane sapphire substrates are used for the hetero-epitaxial deposition of silicon for microelectronic IC applications. Sapphire is an excellent choice for hybrid substrates such as microwave IC's because of its high dielectric constant. In addition, when filmed with an epitaxial silicon process, high speed IC and pressure transducers can be created. Growing thallium, other superconducting components, high impedance resistors, and GaAs are other applications.
*Chemical resistance - high inert and resistance of sapphire makes it's character hard to be changed in most process environments including hydrofluoric acid and the fluorine plasma applications generally in semiconductor wafer processing. Quartz and polycrystalline alumina and other ceramics are damaged and corroded in similar environments.sapphire windows and optics remain free of damaged.
*sapphire will not contaminate during processing.
*Electrical properties - A high, stable dielectric constant with the electrical insulation required for electronic substrates, RF and microwave transmitting windows and tubes.
*Orientation ensures consistent electrical properties.
*Mechanical properties -A high stiffness (modulus),high strength, provides excellent wear resistance for application environments.strong stiffness enable bear high pressures and keep long life use.
*Optical transmission -Ranges from below 0.2 microns, to over 4 microns, combined with the excellent chemical durability, wear resistance, stiffness, and high temperature performance enables sapphire widely used for windows,sensor optics, high performance vacuum systems and other optical applications. used in window and optic applications where the process environment would destroy conventional glass or quartz optics many applications in wavelength regions beyond quartz transmission range no UV solarization.
*Surface treatments - sapphire can be polished to very tight flatness and smoothness for substrate applications and precision mechanical components.
*Thermal properties - with a melting point over 2000 oC, and high thermal conductivity - sapphire is often used in many harsh process environments for a combination of its thermal, chemical, mechanical, and optical properties.
*Wear properties - with high hardness and transparency, sapphire is used for scratch proofing in high wear applications and for precision mechanical components.