EUV and X-ray are at the shortest wavelength region of light spectrum. They have the advantages of high spatial resolution, chemical sensitivity, and large penetration depth. Imaging and spectroscopy techniques based on this wavelength region provide powerful tools for manufacture and observation at nanometer scale and probe the electron characteristics at the inner shell level.

Multilayer coatings are vital reflective optics in the EUV and X-ray region. Due to the short wavelength, the multilayer d-spacing is only a few nanometers which pose a challenge for the design and fabrication. One well-known application is the Mo/Si multilayer with a d-spacing of 7 nm used in EUV lithography at 13.5 nm wavelength. To improve the interface diffusion and roughness, different interface engineering methods were developed which boost the reflectance of Mo/Si multilayer to 70% at near normal incidence. These have been routinely used in the EUV scanners now.  Besides the lithography, short wavelength microscopy and space observation also generate significant demands for high performance multilayer optics. One important field is the “water window” wavelength region (λ≈2.3−4.3nm) which provides a unique imaging contrast between water and carbon for life science research. Related multilayer mirrors, like Cr/Sc, Cr/V, etc., are required for building such a soft X-ray microscope. These multilayers have a layer thickness of less than 1 nm. Thus, a large amount of work is performed to understand the layer growth behavior and how to improve the layer structure. In the hard X-ray region, multilayers continued to work as monochromators and reflectors at grazing incidence. It can provide a much larger bandwidth and photon flux as compared to nature crystals. The one-dimensional multilayer is further combined with two-dimensional nanostructures to enhance its capability to tailor the light both spectrally and spatially.

Subject Matter Level:

• Intermediate - Assumes basic knowledge of the topic

What You Will Learn:

• Basic principles of multilayers working in the EUV and X-ray region
• Typical fabrication and characterization techniques for this kind of multilayers
• Microstructure properties and layer growth behavior of the ultrathin multilayers
• Three dimensional multilayer grating structures

Who Should Attend:

• Optical coating engineers and scientists
• Engineers involved in development of optical coating equipment
• Scientists/engineers who designs optical systems and/or use coated optical components, particularly in the short wavelength region

About the Presenter: Qiushi Huang, Tongji University

Dr. Qiushi Huang received his PhD degree in optics in Tongji University, 2012. He worked in the FOM institute (DIFFER) and University of Twente from 2012 to 2014 as a postdoc. In 2014, he joined the Institute of Precision Optics and Engineering in Tongji University. He is currently an associate professor in Tongji University. He has a broad research experience in extreme ultraviolet and X-ray multilayers, and multilayer-based optics, for synchrotron radiation facilities, space telescopes and EUV lithography applications. He has a publication list of over 50 journal papers in the aforementioned fields.