Far ultraviolet optical properties of MgF2 films deposited by ion-beam sputtering and their application as protective coatings for Al

摘要

Thin films of MgF2 deposited by evaporation is a material widely used for its transparency in the far ultraviolet (FUV) down to similar to115 mn. in this paper the optical properties of ion-beam sputtered (IBS) MgF2 in the FUV are investigated and compared with MgF2 films deposited by evaporation. A slightly higher transparency at the 121.6-nm, H Lyman alpha line was obtained for IBS MgF2 films compared to films deposited by evaporation, which makes IBS MgF2 a promising protective material for Al reflective coatings. Experimental work on Al films that were protected with a thin evaporated MgF2 film followed by an IBS MgF2 film to produce a protective coating with optimum thickness showed a reflectance at 121.6 mn that was higher by about 3% compared to an Al film protected with an all-evaporated MgF2 film. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 16]