ABSTRACT
Composition dependent structural, optical, and mechanical properties of codeposited thin films were studied in the Si-YF(3) and ZnSe-SrF(2) systems. Intrinsic stress varies nonlinearly in both systems. In the Si-YF(3) system, the stress becomes slightly compressive for intermediate compositions, even though it is highly tensile in the pure constituent thin films. In the ZnSe-SrF(2) system, optical scatter and intrinsic stress exhibit abrupt changes at approximately 60-vol % SrF(2), accompanied by a change in the dominant crystalline orientation. Possible structure-property relationships and composition ranges for practical applications of thick films are also discussed.
ABSTRACT
Thin films of several refractory metal oxides and Ge were deposited by pulsed laser evaporation using a TEA CO(2) laser. Films deposited on ambient temperature substrates had a polycrystalline microstructure. Ge films deposited on 300 degrees C substrates were single crystalline. The refractive indices of these films were higher than indices of films deposited by conventional evaporation techniques and were bulk values for HfO(2) and ZrO(2). The crystalline microstructure and high packing density of the films were attributed to the effect of energetic ions in the laser-induced plasma.
ABSTRACT
Intrinsic stress and microstructure of mixed composition films were investigated for several binary systems of IR optical materials. These properties were measured for the entire range of compositions and for mixing obtained by codeposition and by layering of alternate pure components. The variation of stress with composition was observed to be significantly different, depending on the method of mixing. Microstructural analysis revealed a corresponding difference in the grain structure of the films. Low compressive stress films were obtained by coevaporation of high tensile stress materials. These can be used to produce thick and mechanically stable gradient-index optical coatings.
