Introduction

ZrO_xF_y is an interesting material for optical coatings because of its low losses and variable index of refraction, controllable through the values of × and y. Better known are the compounds with one of the variables set to zero; ZrF₄ and ZrO₂. ZrF₄, with an index of 1.5, is used as one of the base materials in the fabrication of infrared transmitting optical fibers, and ZrO₂ is a well-known optical coating material with an index of approximately 2.1 in dense thin film form. ZrF₄is water sensitive, and has not been used for a coating material in pure form. ZrO₂ has been investigated extensively, and has been shown to be improved by ion-assisted deposition using both argon and oxygen ion bombardment. The mixed-bonding films we describe here can have an index from 1.5 to 1.8, and the index can be easily altered during deposition to produce a filter by varying the ratio of ions to evaporant molecules arriving at the surface.