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

Wide band gap crystals doped with trivalent rare earth ions can be used as optical filters and refractive elements for 157-nm photolithography. Applic ations are depending on the structure of the levels of the 4f(n-1) 5d elect ronic configuration. The 4f(n) --> 4f(n -->1) 5d dipole allowed transitions of Nd3+, Pr (3+) and Gd3+ ions in YF3 crystal hosts, in the vacuum ultravi olet region of the spectrum were studied by applying laser-induced fluoresc ence using the molecular fluorine laser at 157 nm, and absorption spectrosc opy. (C) 2001 Elsevier Science B.V. All rights reserved.