Er₂O₃ Coatings on CVD Diamond Window

SemiXicon DiaSemi Advances High-Temperature Reliable Er₂O₃ Coatings on CVD Diamond

At SemiXicon DiaSemi, we continuously focus on improving the reliability of diamond-based optical components for extreme environments. Erbium oxide (Er₂O₃) has long been recognized as an excellent antireflection material for CVD diamond due to its favorable refractive index matching and superior thermal stability. However, in high-temperature applications, the thermal expansion mismatch between Er₂O₃ and diamond can generate significant interfacial stress, potentially leading to cracking or delamination of the coating.

To address this reliability challenge, our engineering team developed an optimized interfacial modification strategy based on controlled surface oxidation.

Using MPCVD-grown, double-side polished single-crystal diamond substrates (7 × 7 × 0.5 mm³), we evaluated two surface preparation routes:

• Conventional acid boiling treatment

• Acid boiling followed by ozone surface oxidation

A ~1.3 μm cubic-phase Er₂O₃ film was deposited at 800 °C via RF magnetron sputtering.

Our results show that the additional ozone treatment significantly enhances diamond surface hydrophilicity and surface energy, enabling:

• Improved interfacial bonding strength

• Enhanced film crystallinity

• Reduced thermal stress concentration

• Superior resistance to 800 °C air thermal shock

• Stable and high infrared transmittance

This simple yet highly effective surface engineering approach substantially improves coating adhesion without introducing complex interlayers or process burdens, making it scalable for industrial production.

Enabling Reliable Diamond Windows for Extreme Applications

High-performance infrared windows used in hypersonic flight systems, high-power laser platforms, and harsh-environment optical sensing demand more than high transmission—they require long-term thermal stability and robust interface integrity.

Through targeted interface engineering, SemiXicon DiaSemi strengthens the Er₂O₃/diamond interface, enhancing coating durability under extreme thermal cycling while maintaining optical performance. This advancement provides a practical pathway toward more reliable diamond-based infrared window solutions for next-generation aerospace, photonics, and defense systems.