Rare-earth plasma extreme ultraviolet sources at 6.5-6.7 nm

We have demonstrated a laser-produced plasma extreme ultraviolet source operating in the 6.5-6.7 nm region based on rare-earth targets of Gd and Tb coupled with a Mo/B(4)C multilayer mirror. Multiply charged ions produce strong resonance emission lines, which combine to yield an intense unresolved transition array. The spectra of these resonant lines around 6.7 nm (in-band: 6.7 nm +/- 1%) suggest that the in-band emission increases with increased plasma volume by suppressing the plasma hydrodynamic expansion loss at an electron temperature of about 50 eV, resulting in maximized emission. (C) 2010 American Institute of Physics. [doi:10.1063/1.3490704]