RESIDUAL-STRESS AND ADHESION IN ION-ASSISTED HAFNIA COATINGS ON GLASS

Thin film mechanical properties are strongly influenced by the feature s of the employed deposition technique. Ion beam-assisted evaporation permits good control of the parameters involved in the process and off ers several advantages in processing coatings with expected performanc e. In this paper, the generation of residual stresses depending on the ion bombardment conditions and their effect on the adhesion behaviour of hafnium dioxide IBAD thin firms were investigated. Stresses, which were tensile or compressive depending on the momentum parameter RE(1/ 2) values, where R is the ion-to-atom arrival ratio and E is the ion e nergy, were measured with a mechanical profilometer by the curvature c hange of the sample before and after the deposition. The scratch test technique was used to evaluate the adhesion failure load (L(c)) of the HfO2 thin films and is correlated with the stress present in the samp les themselves. The analysed samples showed an increase in critical lo ad as the momentum parameter value increased. Moreover, the coating mi crostructure, which also depends on the deposition conditions, was ana lysed by X-ray diffraction in order to investigate the possible correl ation of tensile or compressive stress with the two him structures for different Values of the momentum parameter.