Modifying a substrate material’s properties often requires one or more film coating methods. Various thin-film coating techniques are available, and most involve the deposition of a material onto an optical element’s surface.
Coating methods such as thermal, e-beam, and reactive arc evaporation are cost-effective, but the film quality with these techniques is relatively low. Other techniques, such as ion beam sputtering, offer optimal durability and environmental stability, but at higher costs.
Ion-beam-assisted deposition (IBAD) provides the best of both worlds, with quality depositions and a high return on investment. This article takes an in-depth look at IBAD and how it works.
IBAD Meaning: What Is Ion-Beam-Assisted Deposition?
Ion-beam-assisted deposition, or ion-assisted deposition, is a thin-film deposition method involving ion bombardment and physical vapour deposition (PVD). The IBAD process takes place in a vacuum.[1]
While the PVD technique evaporates the material, an ion source directs high-energy nitrogen and argon ions at the growing thin film.
An ion-beam-assisted deposition system provides independent control of several deposition parameters, including the ion energy, the substrate atoms’ arrival rate, and the temperature. As a result, the thin film properties are manipulable.
Difference Between IBAD (Ion-Beam-Assisted Deposition) and IBID (Ion-Beam-Induced Deposition)
This section provides a comparative analysis of ion-assisted deposition and ion-beam-induced deposition.
IBAD is a thin-film coating process that combines evaporation and ion-assisted e-beam deposition. By directing reactive ions to the surface area, it is possible to control the thin films’ chemical composition, bonding, and morphology.
On the other hand, IBID involves the deposition of fragments onto a substrate near the coating material by using a high-energy ion beam to decompose gaseous molecules.
The IBID method is similar to electron-beam deposition (EBID). However, instead of using an electron beam and scanning electron microscope, an IBID system uses an ion beam.
The Advantages of Ion-Assisted Deposition and High Ion Energy
The ion-assisted deposition process offers several advantages over conventional sputtering and thermal evaporation techniques. The IBAD process is relatively slow compared to traditional PVD methods, but it is the technique that produces precision films of the highest quality.[2]
Ion-Beam Sputtering Produces Stronger Interfacial Adhesion
Directing a beam with a range of ion energies at the substrate improves various performance factors, including adhesion. Adjusting the angle of the beam with the substrate provides a means for controlling the texture of the film surface, ensuring optimal bonding strength between:
- The coating layers
- The coating and the substrate
IBAD makes base material etching possible, which creates an intermix between the base material and coating atoms. The etching process creates a gradual transition from the base material to the coating, providing a stress-free and durable bonding.[3]
IBAD Produces Precision Films of the Highest Quality
IBAD provides control over two parameters:
- Acceleration voltage
- Ion current density
This deposition process achieves a relatively high density because of the ions’ ability to prevent the columnar growth that typically occurs in a growing film. The high-density film deposition offers superior durability in hard coatings.
IBAD Is Ideal for Coating Temperature-Sensitive Materials
During IBAD, the base material temperature can range from 15°C (59°F) to 300°C (572°F). This low temperature range makes IBAD suitable for coating temperature-sensitive materials, such as polycarbonate and other thermoplastic polymers.
IBAD Applications
IBAD is the ideal process for various optical applications that require precision tuning of a coating’s thickness and reflective index. Using IBAD, manufacturers can produce a wide range of thin films and optical coatings, including telescope mirrors.
Other applications of IBAD include the deposition of ceramic materials and metallics, including gold, silver, titanium, and platinum.
Ceramics include aluminium oxide, silicon dioxide, and titanium nitride (TiN) coatings. Machine tool manufacturers often add a TiN coating to milling cutters and drill bits, improving these products’ edge retention and corrosion resistance.[4]
Final Thoughts
Ion-beam-assisted deposition (IBAD) is one of the leading thin-film creation techniques to ensure a high-quality, durable coating. This process involves the bombardment of ions at a base material during a PVD process.
Understanding the applied physics behind IBAD can be very helpful during your next project. To learn more about thin films, please browse through the articles from the Korvus Technology blog.
References
[1] Hsu, S.C., Hong, J.Y., Chen, C.L., Chen, S.C., Zhen, J.H., Hsieh, W.P., Chen, Y.Y. and Chuang, T.H., 2021. The structures and thermoelectric properties of Zn-Sb alloy films fabricated by electron beam evaporation through an ion beam assisted deposition. Applied Surface Science, 540, p. 148264.
[2] Tanaka, I., Matuoka, S. and Harada, Y., 2022. Mechanical properties of amorphous SiCN films deposited by ion-beam-assisted deposition. Diamond and Related Materials, 121, p. 108732.
[3] Jin, J., Chen, D. and Jiang, Z., 2021. Solid lubricating films: Ion beam assisted deposition. In Protective Thin Coatings Technology (pp. 31-57). CRC Press.
[4] Xue, G., Wang, Z., Wang, E., Tang, Y., Zhao, Y., Wang, Y., Hu, S., Xiang, L. and Xie, Z., 2021. Enhanced hot salt-water corrosion resistance of NiCoCrAlY-AlSiY coating by ion-beam-assisted deposition. Coatings, 11(9), p. 1062.
