nOPTO™ - Beneq ALD coatings for the optical and photonics industry
The are several reasons for using ALD in optical and photonics applications. Firstly, ALD enables coating objects that are difficult or impossible to coat by other methods. Secondly, ALD gives you free hands to engineer novel optical materials. Thirdly, the accuracy of the film thickness in ALD is usually 0.2 to 12 Å, depending on the material. And last but not least, ALD coatings are completely conformal and pinhole-free, making them especially suitable for barriers and passivation layers. Beneq nOPTO™ now offers ALD coatings for the optical and photonics industries.
Tailored, engineered materials
The ability to engineer novel materials is one of the strongest features of ALD. ALD is especially capable of making materials that require mixing of atoms and thin layers. Doping is easy with ALD. Many possibilities for dopant materials exist, including rare-earth elements.
Modified TiO2 is a good example of a versatile ALD material. The film is intrinsically an optically amorphous, physically crystalline, high-index and low-loss optical film. TiO2 has a high refractive index, but above 150 °C it turns crystalline, causing scattering and optical losses. Scattering from crystals can be prevented by keeping the crystal size small. This can be done by depositing an amorphous ALD thin film between the crystalline layers. The index is kept high by using a < 1 nm amorphous layer.
A well-known ALD application is the thin film electroluminescence (TFEL) display. In the display, light is generated in a Mn-doped ZnS phosphor layer. The insulators are engineered materials made from Al2O3 and TiO2 with ALD.
Densely-colored films add life and character to commercial objects and devices with stringent requirements for aesthetic values. Dielectric, non-conductive, metal-looking mirrors can be deposited on plastic materials.
ALD provides the best available barrier layers due to its conformal, pinhole-free film growth. A good example of this is Beneq nSILVER® anti-tarnish coating for silver jewelry, which is a dense, optically transparent and conformal barrier layer invisible to the human eye.
ALD is a mature technology. Globally, most ALD coating activities are within the semiconductor market, where films are thin. Optical applications and many other industries usually require coatings that are several micrometers in thickness. As a technology, ALD has no difficulties in depositing thick films. For processing continuously thick films, however, an industrial ALD coating system has to be designed and built for that purpose. Beneq ALD systems are thoroughly industry-proven for providing reliable and repeatable processing of film stacks many micrometers thick.
Download nOPTO brochure (pdf).