Search for High-Strength Multilayer Free-Standing Film Filters with High Transmittance in the Wavelength Range of the “Water Window” (2.3–4.4 nm)

Some variants of the composition of multilayer absorption film filters with a high transmittance in the spectral region of the “water window” (2.3–4.4 nm) have been considered. Having created an ultimate pressure difference between the sides of free-standing films at which they are damaged, we compared the strength of 100 nm thick Ti-based multilayer filters with Al, Be, C interlayers and 100 nm thick V-based multilayer filters with Al interlayers. Sc and Cr was also considered as interlayers. Among the tested periodic multilayer structures, the best strength characteristics were demonstrated by Ti/Be (with a fraction of Ti in a period of about 0.6) and V/Al (with a fraction of V in a period of about 0.4) multilayer filters. Despite the fact that Ti/Be and V/Al filters are inferior in strength to Ti and V monolayer filters of the same thickness, these multilayer filters may be of interest, since they have either a higher transmittance in the “water window” (Ti/Be) or more high level of blocking of visible radiation (V/Al).