Multilayer coatings for narrow-band imaging in the extreme ultraviolet

Multilayer coatings for the extreme ultraviolet with high reflectance at a spectral band of interest and zero reflectance at another band to be suppressed have been designed and prepared. Multilayer coatings were designed to maximize normal-incidence reflectance at the O+ 83.4-nm spectral line and to suppress at the same time radiation at the 121.6-nm hydrogen Lyman alpha line. Fresh Al/MgF2/Mo multilayer coatings resulted in high reflection/suppression ratios at the above wavelengths. The coatings also exhibited a dip in reflectance at 102.6-nm Lyman beta. The coatings showed some slow but steady degradation over time that could be partially eliminated by sample cleaning. Al/MgF2/Mo multilayer coatings protected with a thin ion-beam-deposited C film were found to give a high reflection/suppression ratio with lower degradation over time. (C) 2001 Optical Society of America