Consequence of Nanometer-Scale Property Variations to Macroscopic Properties of CrOCN Thin Films

Authors


  • J. J. Petrovic—contributing editor

  • This work was supported by the National Science Foundation, by the GAOLI Program, and by Central Research, DuPont Company. The facilities used were supported by the MRSEC program under Grant No. DMR 91-20668.

Abstract

Macroscopic properties of CrOCN thin films are related directly to composition and property variations on multiple length scales. Compositions resolved on a nanometer scale were measured in-depth in 120–150 nm thick CrOCN films by sputtered neutral mass spectroscopy. A statistical analysis of composition identifies the particular coordinations of the various anions with Cr that form preferentially under relevant processing conditions. Near-edge structure in electron energy loss from transmission electron microscopy and the Cr core level shift in X-ray photoemission spectroscopy further support this conclusion. A wide range of compositions are described in terms of mixtures of binary and ternary compounds, and optical absorption is found to be correlated with the presence of Cr4+ within this description. It appears that the presence of the unfilled t2g state is responsible for optical absorption in the range of 0.5–6 eV and that a critical concentration of Cr4+ in certain species within the system is required for the transition to occur. These results conflict with the suggestion that a percolated network of metallic clusters is responsible for the change in properties.

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