Nitrogenated nanocrystalline diamond films: Thermal and optical properties

Ultrananocrystalline diamond films have been grown by microwave plasma CVD using CH4/H-2/Ar mixtures with N-2 added in plasma in amounts up to 25%. The films were characterized with AFM, Raman, XRD, and UV-IR optical absorption spectroscopy mainly focusing on optical and thermal properties. In comparison with polycrystalline CVD diamond the UNCD are very smooth (R-a < 10 nm), have low thermal conductivity (similar to 0.10 W/cm, K), high optical absorption (similar to 10(3) cm(-1) at 500 nm) and high concentration of bonded hydrogen (similar to 9 at.%). The nitrogen presence in the plasma has a profound impact on UNCD structure and properties, particularly leading to a decrease in resistivity (by 12 orders of magnitude), thermal conductivity, Tauc band gap, optical transmission and H content. The UNCD demonstrated rather good thermal stability in vacuum: the diamond phase still was present in the films subjected to annealing to 1400 degrees C. (C) 2007 Elsevier B.V. All rights reserved.