Focused Ion Beam (FIB) tomography of nanoindentation damage in nanoscale metal/ceramic multilayers

A serial sectioning approach using dual beam FIB (focused ion beam) technique was used to visualize damage in 3D after nanoindentation of Al/SiC multilayered composites. Al/SiC multilayer was deposited on a Si (111) substrate using magnetron sputtering. A total of 41 alternating layers of Al and SiC were deposited with a target thickness of 50 nm for each layer. A Berkovich diamond indenter was used to indent the sample. The indentations were analyzed under a Scanning Electron Microscope (SEM) and cross-sectioned using a Focused Ion Beam (FIB) to study deformation under the indentation. Because of the symmetry of the indenter, reconstruction of 1/3 of the indentation was sufficient to quantify the damage under the indenter. Before the sectioning process, a 500 nm thick Pt layer was deposited on the indentation area. It was found that otherwise brittle, SiC in nanolaminate form, exhibits high flexibility. The fracture in SiC layers was attributed to the complex stress state that develops in the indented region and leads to areas of high shear stress where fracture occurs.