Highly reflective Cr/C-based multilayer X-ray mirrors for the wavelength λ = 4.47 nm

Area of Science:

• Materials Science
• Optics
• X-ray Physics

Background:

• Multilayer X-ray mirrors are crucial for applications in the soft X-ray spectrum.
• Optimizing mirror performance requires understanding and controlling interfacial properties.
• The carbon transparency window (4.4-6.6 nm) is important for various spectroscopic techniques.

Purpose of the Study:

• To investigate the structural and reflective characteristics of Cr/C multilayer X-ray mirrors.
• To optimize these mirrors for the "carbon transparency window" spectral range.
• To improve the reflection coefficient through interface engineering.

Main Methods:

• Fabrication and characterization of Cr/C multilayer structures.
• Analysis of interlayer interface characteristics using surface-sensitive techniques.
• Interface engineering via nitrogen passivation of carbon layers.
• Measurement of reflectivity at normal incidence for specific wavelengths.

Main Results:

• Interlayer interfaces at the Cr-on-C boundary were found to be more extended than at the C-on-Cr boundary.
• Nitrogen passivation reduced the Cr-to-C interface size from 0.51 nm to 0.39 nm.
• A record reflection coefficient of R = 20.2% was achieved at a wavelength of λ = 4.47 nm.

Conclusions:

• Interface engineering, specifically nitrogen passivation, is effective in enhancing the performance of Cr/C multilayer mirrors.
• The optimized mirrors demonstrate superior reflectivity within the carbon transparency window.
• These findings contribute to the development of advanced X-ray optical components.