Optical Coatings
Optical Thin Films
Thin films can offer a wide variety of effects on the properties of the substrate they are deposited on, one of these such changes, can be the way that the substrate reacts to light. Optical coatings are used to modify the existing reflectance or transmittance of a given sample to make it a better fit for its application.
Two optical thin-film coatings that are commonly used are antireflective and high-reflection or mirror coatings.
Indium Tin Oxide (ITO)
Many day-to-day items rely on transparent, conductive coatings to operate from windshields to touch screens. Glass in its pure form is not a great conductor or either heat or electricity and so for certain applications – a thin layer of material is needed to improve this, while maintaining the transparent nature of the substrate.
Indium Tin Oxide (ITO) Coatings can be used in these cases and are regularly used in various fields. It can greatly alter the properties of glass, mylar or other transparent substrates when deposited as a thin film with its main benefits being the improvement of the conductivity and the refractive index of the deposited upon glass.
The thickness of the coating can vary depending on the application, with a thicker ITO layer offering a greater conductance, but increasing its opacity. They can also prove to be very stable under heat loads of below 150C.
Another key aspect of an ITO coating is its resistance to electromagnetic wave penetration; therefore, ITO coated substrates can be key features of windows that require EM radiation protection but must retain its transparency.
Sputtering or E Beam
ITO films can be deposited onto substrates via CVD, ink polymer-resin processes and most commonly through PVD. Korvus Technology has over 20 years of experience working within the PVD field and is the manufacturer of the HEX series of PVD instruments. These tools can be configured to allow for the optimized deposition of ITO coatings through DC magnetron sputtering and E-Beam evaporation.
Due to the conductive nature of ITO material, DC magnetron sputtering processes can be used to achieve high levels of uniformity across various wafer and substrate sizes. We recommend using the Korvus-custom tiltable FISSION 3’’ magnetrons to curate a balance between uniformity, target usage and deposition rate suitable to your process. Altering the source to sample distance is also crucial for ITO deposition to control the electron interactions between the generated plasma and the sample.
If you are interested in ITO deposition, please feel free to get in touch and enquire about how Korvus Technology can future-proof your lab – sales@korvustech.com
Frequently Asked Questions
How is PVD used for optical coatings?
Optical coatings in PVD (Physical Vapour Deposition) are thin layers of material deposited onto optical components—such as lenses, mirrors, or filters—to modify how they interact with light. These coatings are engineered to enhance or suppress reflection, transmission, absorption, or polarisation at specific wavelengths.
How does reactive sputtering in PVD Work?
Reactive sputtering refers to the process of introducing an additional ‘reactive’ gas alongside the inert process gas during a deposition run. Common gases used for this are oxygen, nitrogen, ammonia and acetylene due to their tendency to form compounds with other materials when under process conditions.
The reactive gas interacts with the vapour flux of the sputtered material and forms compounds that will settle as films on the desired substrate. Oxygen for example, would react with some metals and form an oxide layer film.
Reactive sputtering is a process common in PVD and can be achieved in the Korvus Technology HEX Series through the use of multiple MFCs and the FISSION magnetron source.
How is PVD used for optical coatings?
Materials (like oxides, metals, or nitrides) are vaporised in a vacuum chamber, using any one of the PVD deposition techniques. The vapour then condenses on the optical substrate, forming a thin film.
Common PVD techniques for optical coating deposition include thermal evaporation, electron beam evaporation, and sputtering.
What type of optical coatings are used in PVD?
Anti-Reflective (AR): Reduces surface reflections and glare.
High-Reflective (HR): Maximises reflection for mirrors.
Beam Splitters: Transmit part of the light and reflect the rest.
Bandpass Filters: Transmit only a specific wavelength range.
What materials are used for optical coatings in PVD?
Dielectrics like SiO₂ (silicon dioxide), TiO₂ (titanium dioxide), or MgF₂ (magnesium fluoride)
Metals like aluminium, silver, or gold for reflective coatings