THERMAL STABILITY OF RF-SPUTTERED AMORPHOUS FILMS IN COMPARISON WITH GELS IN THE SiO2-ZrO2 SYSTEM

Amorphous-forming regions in the RF-sputtered SiO2-ZrO2 films determined by X-ray diffraction were in the range 0-70mol%ZrO2 under sputtering power 50W, sputtering time 15h and in the range 0-68mol%ZrO2 under sputtering power 100W, sputtering time 25h with Ar/O2=3 atmosphere. Crystallization temperatures, TC, measured by DTA on the sputtered films decreased with increasing ZrO2 content. From the liquidus temperature, TL, of the system the thermal stability of the sputtered films was evaluated in terms of TC/TL ratio, which means the amorphous-forming ability, ability of the system to form an amorphous phase. TC/TL ratio decreased with increasing ZrO2 content from 0.81(0mol%ZrO2) to 0.36 (69.1mol%ZrO2) in the sputtered films. Gels of the SiO2-ZrO2 system were prepared from Si(OC2H5)4 and Zr(OC3H7)4 ethanol solution with or without water addition in the range 0-100mol%ZrO2. TC was measured on dried and calcined gels by DTA. The thermal stability, TC/TL, of gels was found to decrease from 0.77(0mol%ZrO2) to 0.23 (100mol%ZrO2). The compositional dependence of TC/TL ratios of gels was almost comparative with those of the sputtered films, implying that amorphous-forming ability is intrinsic to the system.