Boron and silicon: filters for the extreme ultraviolet

Thin films of boron and silicon have been developed using electron beam deposition. The transmissions of these filters were measured from soft x-ray wavelengths to the far ultraviolet and at optical wavelengths. The boron filter transmission peaks near 66 Å and the silicon filter peaks near 136 Å as expected on theoretical grounds, but the extreme ultraviolet bandpass is narrower than expected. The peak transmission of these filters does not change with time, but the width of the silicon filter bandpass is reduced slightly as the filter ages.