Improved adhesion of gold coatings on ceramic substrates by thermal treatment

The influence of thermal treatment on the adhesion of thin gold films on Al2O3 ceramic substrates has been investigated by scratch test measurements. The adhesion was found to be substantially increased when the systems were heat-treated at 500°C, and the adherence depends on the length of treatment. An attempt to explain the improved adhesion was made by using X-ray photoelectron spectroscopy (XPS) to study the Au/Al2O3 interface in both untreated and treated samples. Analysis of the core level spectra of Au, Al and O recorded in the interfaces showed reactions between gold and aluminum in both cases. Compared to untreated samples, the interdiffusion of both species at the interface of the treated sample was critically important. In addition, the formation of new compounds was also observed. The improvement in mechanical adherence of gold thin films on the ceramic substrate is explained by the formation of gold aluminum compounds and gold oxide in the interfacial region.