The surface and layer state of thin ion-beam-irradiated Au-Al layers was investigated with scanning high-energy ion microscopy (SHEIM), RBS and SEM. The thin metal layers (90 nm Au top layer and 200 nm A layer deposited on polished glassy carbon) were produced by evaporation and subsequently irradiated with 2.0 MeV 4 He + ions (ion current 300 nA; beam spot diameter 0.5 mm) to initiated the Au-Al interdiffusion process in the layered structure. In situ RBS measurements were performed during irradiation. Both SEM and SHEIM (three-dimensional mapping) analysis of as-deposited and ion-beam-irradiated specimens showed the stability of the separated and interdiffused layers. Voids in the interdifused Au-Al layer and at the specimen surface were not observed.