Diamond nucleation on iridium: Local variations of structure and density within the BEN layer

The diamond nuclei generated by the bias enhanced nucleation (BEN) on iridium are gathered in well defined areas (“domains”). In atomic force microscopy (AFM) measurements they become manifest in a 1 nm downward step. The fine structure of the carbon layer inside and outside these domains has been studied by small spot Auger electron spectroscopy (AES), high resolution transmission electron microscopy (HRTEM), AFM and lateral force microscopy (LFM). The Auger spectra of the carbon KLL peak taken in an ultra high vacuum setup revealed diamond features inside and more graphitic features outside the domains. The comparison with the intensity of the Auger signal originating from the underlying Ir film indicates a carbon coverage inside the domains which is only by about 20% lower than outside. Cross section HRTEM images after BEN and after a short growth step, as well as AFM measurements after softly etching off the carbon layer, give no indication that the Ir had experienced a major modification by the domain formation process. Combining the information deduced from these experiments we conclude a significantly higher density of the carbon matrix within the domains. The lower friction forces measured in these regions by LFM confirm the interpretation of a material with higher elastic modulus. The present results allow to refine our understanding of structure and formation of the BEN layer on Ir.