Focused ion beam-secondary ion mass spectrometry analyses of nanostructured thin films

Focused ion beam-secondary ion mass spectrometry (FIB-SIMS) with spatial resolution down to 20 nm was used to analyse thin carbon and titanium oxide films, from the micro- to nanoscale level. Amorphous carbon films were produced both by a plasma assisted chemical vapour deposition (PACVD) system from different mixtures of acetylene and tetrafluoromethane and cluster assembled from graphite cathodes, in a He atmosphere, using a supersonic cluster beam apparatus. With the same apparatus, titanium oxide films were obtained with a titanium cathode, in an oxygen atmosphere. We acquired mass spectra and ion imaging of film surfaces. Contaminant distributions along the depth and on the surface were investigated. We found Na, Ca, K, Cl, due to atmosphere contamination; their distribution is homogeneous along the surface and decreases rapidly with film depth, showing that no contaminants percolate into the film. Mass spectra highlight the mass distribution; in particular, cluster mass distribution from cluster-assembled films is shown. Surface images show the secondary ion distribution for F-, Cl-2(-), Ti+ and other ion compounds. Compositionally heterogeneous regions are evident mainly along defects, such as edges, on the film surface, where the images show preferential accumulation of some elements.