Evolution of Residual Stress and Structure in YSZ/SiO₂ Multilayers with Different Modulation Ratios

The multilayer (ML) YSZ/SiO₂ films with different modulation ratios ranging from 1:3, 4:9, 1:1 to 3:1 (the thickness ratio of the YSZ to SiO₂) are deposited on BK7 glass substrates by electron beam evaporation under the same processing conditions. The effect of modulation ratio on the residual stresses and structure are investigated by an optical interferometer and Grazing incidence x-ray diffraction. The results show that the total residual stress in MLs is compressive and decreases to tensile when the modulation ratio is changed from 1:3 to 3:1. The YSZ films are of cubic phase structure and the SiO₂ films are amorphous in all the MLs. The change of residual stress in these MLs can be attributed to the variation of an individual layer?s stress with thickness, which indicates that adjusting the thickness ratio of two materials is an effective measure for depositing near-zero stress MLs.