Titanium oxide/aluminum oxide multilayer reflectors for “water-window” wavelengths

Twenty bilayers of titanium oxide and aluminum oxide with the layer-pair thickness of 4.43 nm on a silicon substrate were fabricated for novel multilayer reflectors at water-window wavelengths by an atomic layer deposition method of controlled growth with sequential surface chemical reactions. The high reflectance of over 30% at a wavelength of 2.734 nm and an incident angle of 71.8° from the normal incidence was demonstrated experimentally. The full width at half-maximum of the reflectances at 2.734 nm was 0.0381 nm, which corresponds to Δλ/λ=1.4%.