A microstructural study of superconductive nanocrystalline diamond

A transmission electron microscopy (TEM) study of superconducting nanocrystalline diamond (NCD) continuous layers is reported. The high resolution transmission electron microscopy (HREM) and the diffraction contrast modes of observations are used to reveal the nanograins configuration. Three types of them are observed: first, close to the interface with the Si/SiO2 substrate, 10–20 nm-sized diamond seeds resulting from the 5 nm size diamond powder deposition before growth that show some regrowth during CVD process, second a diamond overgrown layer, quasi-epitaxially by coalesced larger NCD grains, and finally, up to the free surface, a thin disordered region composed of nanocrystallites smaller than 6 nm. This last layer was not nominally expected and is attributed to a renucleated-like (RND) carbon layer embedding ultra NCD grains. Diffraction contrast observations confirm this HREM observed behavior.