Characterization of the core structure of growth defects in CVD diamond films by UHREM : Z-shaped twin interactions

We report here recent electron microscopy observations of defect core structures in diamond thin films prepared by microwave plasma-assisted chemical vapour deposition (CVD) on silicon substrates. The defects have been identified by ultra-high resolution electron microscopy (UHREM) at 0.15nm resolution. These results clearly reveal the core structure of two particular fault systems arising from the zig-zag shaped interaction between three nanotwin lamellae, with the occurrence of one as yet unreported structural unit of octagonal type. We analyse the UHREM images of these complex defect configurations and we propose plausible 3D models for each of them, on the basis of image-matching with computer simulations. The identification of these defect structures with growth defects provides valuable insights into the mechanisms involved in the CVD production of diamond films