Influence of Aging Processes on Adhesion Properties of Metallic and Oxidic Thin Films

Abstract

AbstractAdhesion of oxidic and metallic films with thicknesses between 40 nm and 350 nm has been investigated by means of a scratch-test method based on a vibrating diamond micro-indenter. SiO2 and TiO2 films are precipitated on fused silica substrates by sol-gel techniques (SG), reactive evaporation (RE), reactive low-voltage ion plating (IP), and plasma impulse chemical vapour deposition (PICVD), and Cr-layers are produced by rf magnetron sputtering (SP). The influence of aging effects on film adhesion is investigated in respect of several conditions, like storage under ambient surroundings with differences in relative humidity or temperature treatment. A method is presented allowing control of the long-term stability of the scratch-test conditions. Temperature treatment up to 600 °C is found to have the most significant impact on adhesion properties. Adhesion increases for some SiO2 films, whereas for TiO2 layers an opposite behavior is observed. Here, the adhesion of the originally amorphous titania films is reduced due to the phase transition to polycrystalline anatase, which correlates with a significant increase in film stress.