Soft X-ray imaging with coherence tomography in the water window spectral range using high-harmonic generation

Area of Science:

• Physics
• Materials Science
• Imaging Technology

Background:

• High-harmonic generation (HHG) provides coherent extreme ultraviolet radiation suitable for imaging.
• Previous limitations in efficiency scaling hindered soft X-ray imaging applications.
• The water window (284–532 eV) offers unique elemental contrast for materials analysis.

Purpose of the Study:

• To demonstrate the feasibility of HHG for imaging in the water window spectral region.
• To achieve nondestructive depth profile imaging of heterostructures.
• To utilize a lab-scale HHG source for advanced soft X-ray imaging.

Main Methods:

• Soft X-ray Coherence Tomography (SXCT), a Fourier-based technique adapted from Optical Coherence Tomography.
• Utilizing a high-flux, lab-scale HHG source covering the entire water window.
• Achieving high axial resolution (12 nm) by leveraging the full source bandwidth.

Main Results:

• Demonstrated nondestructive depth profile imaging in a heterostructure.
• Successfully imaged layered structures of Aluminium oxide, Platinum, and Zinc oxide.
• Achieved a photon flux exceeding 10^6 photons/eV/s at 500 eV.

Conclusions:

• HHG is a viable source for water window imaging applications.
• SXCT provides a broadband, noise-resistant method for nanoscale depth profiling.
• The developed technique validates findings using electron microscopy.