Sapphire (Al₂O₃) Material Properties
We offer a wide range of Al₂O₃ substrate sizes beyond those listed above, from 5x5mm to 4-6 inch (largest Al₂O₃ size depending on orientation).
Single crystal sapphire Al₂O₃ is chemically stable, electrically insulating, hard, temperature resistant and has high transparency in the UV-Visible wavelength range. It is easy to make in large crystals and due to its very high hardness it is possible to polish them to an atomically flat surface. As such it is a common choice for the growth of many thin films as well as other uses in and around the lab as a cheap, reliable flat surface.
As Al₂O₃ is highly transparent (>85% in near UV-Visible-IR range 0.17 to 5.5 μm), it is commonly purchased double side polished so that you can perform transmission / absorption spectroscopy on thin films. But for any other use can be purchased single side polished.
Sapphire (α-Al₂O₃) as a hexagonal structure, belonging to the space group R3c, can be expressed both as a hexagonal (4 indices hkil) or as a rhombohedral unit cell (hkl). The Al atoms are octahedrally coordinated by six oxygen atoms. The oxygen ions nearly form a hexagonal close-packed structure with aluminium ions (Al3+) filling two-thirds of the octahedral interstices. Each Al3+ center is octahedral.
Sapphire (Al₂O₃) Planes
The figure below shows the common planes of Sapphire and those available from Crystal Substrates. C-Plane and A-plane are the most commonly used in the lab, but each have their use for stabilizing growth of specific orientations of thin film materials.
- C-plane (0001): The most common orientation used for epitaxial growth of GaN in LED manufacturing, offering a hexagonal surface that aligns well with wurtzite-structured materials.
- A-plane (11:20): Provides an orthogonal surface to the c-axis, often used in optoelectronics and photonics for its unique anisotropic properties and lower thermal expansion mismatch with certain materials.
- R-plane (11:02): Features a rhombohedral surface, commonly employed in the growth of silicon carbide (SiC) and for applications requiring unique birefringent properties.
- M-plane (10:10): Used in the fabrication of non-polar and semi-polar GaN devices, offering a reduced electric field effect in optoelectronic applications, which can improve performance in LEDs and lasers.
- M-plane (10:14): A specific orientation within the M-plane family, utilized in applications requiring particular crystal orientations for specialized optical and electronic properties.
Commonly grown materials on sapphire (Al₂O₃) substrates:
ZnO, β-Ga2O3, AlN, GaN, CuGaO2, TiO2, LiCoO2, Spinel battery materials.
There is too much information out there on sapphire substrates and their uses to summarise here fully but if you have any questions, feel free to get in contact at info@crystal-substrates.com.
Dr Joseph Franklin
