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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.

We present a comparative study of C-terminated and Si-rich 3C–SiC(100) surfaces exposed to a H2/CH4 microwave plasma used in diamond growth. Each surface is characterized before and after short plasma exposures using LEED, XPS and STM techniques. In both cases, a 5 minutes plasma exposure led to a 1 × 1 LEED pattern associated with a slight oxygen contamination as evidenced by XPS. However, upon additional annealings, the two surfaces exhibit very different behaviors. For the Si-terminated 3 × 2 surface, a 1 × 1 → 2 × 1 transition occurring at 1173 K is observed while the initial c(2 × 2) surface reconstruction is restored at 1323 K for the C-terminated surface. Furthermore, the XPS measurements show a correlation between oxygen surface release and LEED transitions. An atomic arrangement is observed by STM for the C-terminated surface (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An elucidation of the core structure of fivefold twin centres arising from the interaction between less than five first-order twin boundaries in plasma-assisted chemical vapour deposition (CVD) of diamond films is reported. These particular twinning centres have been identified by ultra-high resolution electron microscopy at 0.12nm resolution, with the help of image calculations. Plausible three-dimensional atomic-scale models are proposed for two specific structural variants, which have been found closely connected to high-order twin boundaries via original heptagonal or octagonal structural units. To our knowledge, this is the first time that such types of fivefold twin centres and associated structural units, which are quite representative of the growth defects observed in CVD diamond, have been reported.