Al2O3 | Optical characterization of thin films

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Aluminum oxide as Al2O3 is one of the most popular thin film materials because of its wide transmittance range and practical price point for mass production. This pure Al2O3 is designed to require a reduced preconditioning time before deposition. Several research reports have proved that our aluminum oxide is superior to standard Al2O3 for thin film coating in term of the following:

Melting speed

The time spent for preconditioning the material is surely an important factor when considering production efficiency. During this process, films are not deposited, but the process is still necessary. Compared with ordinary Aluminum oxide, our Al2O3-Supreme has a unique sintered structure allowing faster melting of the surface.

Less out-gassing

Out-gassing during deposition severely reduces thin film quality. So to avoid this, we ensure that all the gas in the material is removed during preconditioning, or we simply use a lower deposition rate. However, by changing the structure of the material to reduce the volume of voids, out-gassing is decreased and melting is easier, thereby reducing the required irradiation time for heating, as the excess heating required by ordinary materials is another possible cause for out-gassing.

Aluminum oxide: Al2O3 sintered-type product Thin film properties of Al2O3 Refractive index: 1.64 at 550 nm Transmittance range: Evaporation source: Compatible crucibles: Type of deposition: Film stress: Major applications: Physical properties of Aluminum oxide (Al2O3) Theoretical density: Melting point: Water solubility/Chemical resistance: Crystal structure: Electric resistivity: Dielectric constant (relative permittivity): Coefficient of thermal expansion:

Product information

Al2O3 is known as a moderate-index material that has a wide transmittance range from the VUV to the IR region. Its refractive index is near 1.64 at 550 nm, and its transmittance range is from below 200 nm to 7 μm. Al2O3 thin films have good adhesion, hardness, durability, and anti-wear properties. These characteristics make it popular in various applications: a well-known basic anti-reflection coating for the VIS region is a three-layered coating with the structure "substrate/Al2O3/ZrO2/MgF2/air." Al2O3 has a high melting point and is usually evaporated by an electron beam. Al2O3 films have an amorphous structure, with good shielding properties against water vapor.

Two types of Al2O3 evaporation materials are available in the market: sintered Al2O3 and fused crystalline Al2O3. The sintered type tends to have a porous structure, in contrast to the crystalline structure of the fused type. And it is often pointed out that the sintered type tends to emit more gas, but this also depends on sintered structure of the material. Sapphire and other hexagonal crystals (corundum) with indices near 1.76 are the principle bulk forms of alumina. In thin-films, Al2O3 has an index of 1.6-1.65.

Often, the poor level of deposition control in terms of film uniformity and deposition rate afforded when using electron beam evaporation for depositing Al2O3 has contributed to the frustration of working with this material. However, we specially modify the sintered structures of our Al2O3 materials to specifically address these problems. However, the best material for production or experimentation also depends on your priorities: for example, to increase the production speed by increasing the deposition rate, materials that can endure the high deposition rate will be required. Our pellet- and arch-type Al2O3 deposition materials are designed specifically for this purpose. In addition, as a more cost-effective alternative to Al2O3 fused materials that offers greater deposition control, we recommend our Al2O3 Supreme product, which is a sintered granule-type Al2O3 that can be melted more easily than fused or crystalline Al2O3.