Fabrication of buried nanostructures with flat surface by ALD

Rizwan Ali, Muhammad Rizwan Saleem, Matthieu Roussey, Jari Turunen & Seppo Honkanen Scientific Reportsvolume 8, Article number: 15098 (2018) 

We present a method for fabricating buried nanostructures by growing a dielectric cover layer on a corrugated surface profile by atomic layer deposition of TiO2. Selecting appropriate process parameters, the conformal growth of TiO2 results in a smooth, nearly flat-top surface of the structure. Such a hard surface can be easily cleaned without damage, making the nanostructure reusable after contamination. The technique has wide applicability in resonance-domain diffractive optics and in realization of quasi-planar metamaterials. We discuss design issues of such optical elements and demonstrate the method by fabricating narrow-band spectral filters based on the guided-mode resonance effect. These elements have strong potential for, e.g., sensing applications in harsh conditions.