Highly reflective Ru/Sr multilayer mirrors for wavelengths 9-12 nm

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Multilayer coatings are crucial for advanced optical applications.
• The spectral range of 9-12 nm is important for solar astronomy and beyond extreme ultraviolet (BEUV) lithography.
• Achieving high and stable reflectivity in this range is challenging.

Purpose of the Study:

• To investigate Ruthenium/Strontium (Ru/Sr) multilayer coatings optimized for the 9-12 nm spectral range.
• To evaluate the reflectivity and stability of these coatings.
• To explore their potential for solar astronomy and BEUV lithography.

Main Methods:

• Fabrication of Ru/Sr multilayer coatings.
• Optical characterization of reflectivity using near-normal incidence measurements.
• Assessment of reflectivity stability over time in ambient air conditions.

Main Results:

• Near-normal incidence reflectivity of up to 62.3% at 11.4 nm was measured immediately after synthesis.
• Reflectivity decreased to 56.8% after five days, then stabilized.
• A reflectivity of 48.6% at 9.34 nm was maintained after two months of air storage.
• This represents the highest reflectivity reported to date for this spectral range.

Conclusions:

• Ru/Sr multilayer coatings show significant promise for applications in solar astronomy and BEUV lithography.
• The coatings exhibit high initial reflectivity and reasonable stability in air.
• Further optimization may lead to even higher reflectivity values.