Thin film characterization by atom probe field ion microscopy

We have demonstrated that the atom probe field ion microscope (APFIM), with its resolution and single atom detection capability, is a potentially valuable thin-film characterization tool for both structural and compositional analysis. APFIM results for a range of thin films deposited onto Mo FIM tips by rf sputtering show details of void network structures, local ordering in amorphous materials, and atomic clustering effects. For instance, large (∼100–300 Å diameter) isolated voids are seen in WO3 and Ge films while smaller (∼10–100 Å) interconnected voids appear in the metallic films investigated (Ni, Pt, Au). Layer-by-layer depth profiling of atomic structure and selected area (10–30 Å diameter) compositional analysis for each layer are possible by pulse evaporation. From these latter experiments the existence of ion clusters is clearly established.