SummaryA new technique for the three-dimensional analysis of subsurface damage of nanocomposites is presented. Cu±Al multilayers, grown epitaxially on (0001)Al 2 O 3 single crystals by ultra high vacuum molecular beam epitaxy, have been deformed by nanoindentation. Systematic slicing and imaging of the deformed region by focused ion beam microscopy enables a 3D data set of the damaged region to be collected. From this 3D data set, profiles of the deformed sub-surface interfaces can be extracted. This enables the deformation of the individual layers, substrate and overall film thickness to be determined around the damage site. These 3D deformation maps have exciting implications for the analysis of mechanical deformation of nanocomposites on a sub-micrometre scale.

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A new method has been developed to map cracks in 3D using focused ion beam (FIB) microscopy. Using the FIB, many parallel 2D slices are cut in the specimen. Imaging each 2D slice down several directions enables the 3D co-ordinates of features in the slice to be determined. Computer alignment and reconstruction of the 2D slices generates a 3D data set of the analysed zone. The 3D mapping method has been applied to the analysis of the cracks around an indentation site in a Al2O3-5vol.%SiC nanocomposite. This reveals the 3D location and morphology of radial and deep lateral cracks at the indent periphery, surface localised crack clusters, and a crack deficient zone close to the indent centre.

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A novel technique has been developed to examine site-specific, subsurface microstructures in three dimensions. A 3D data set is collected by successive cross-sectional slicing using a gallium focused ion beam (FIB) and imaging using ion-induced secondary electrons, enabling a 3D microstructure map to be generated using computer-based reconstruction techniques. In the first instance, this 3D FIB mapping technique has been applied to copper-based epitaxial metal multilayer coatings which have been deformed by nanoindentation. It is possible to produce 3D profiles of the deformed subsurface interfaces. These individual interface maps allow analysis of the deformation in terms of both the thickness of individual layers and that of the entire film. Material flow, which is seen as pile-up and residual indent zones around the indent, can thus be precisely characterised. The site at which the sectioning is to be carried out can be chosen with high spatial resolution; consequently, nanoscale mechanical properties can be linked directly with an area's microstructure.In an attempt to examine the errors involved in this 3D mapping method the 3D FIB map of the surface of a residual indent has been compared to an atomic force microscopy (AFM) scan of the same region. The sources and significance of the errors are discussed with reference to ways in which they might be reduced.