YF3:Nd3+, Pr3+, Gd3+ wide band gap crystals as optical materials for 157-nm photolithography

Abstract Wide band gap crystals doped with trivalent rare earth ions can be used as optical filters and refractive elements for 157-nm photolithography. Applications are depending on the structure of the levels of the 4f n −1 5d electronic configuration. The 4f n →4f n −1 5d dipole allowed transitions of Nd 3+ , Pr 3+ and Gd 3+ ions in YF 3 crystal hosts, in the vacuum ultraviolet region of the spectrum were studied by applying laser-induced fluorescence using the molecular fluorine laser at 157 nm, and absorption spectroscopy.