Abstract
Hard X-ray photoemission spectroscopy (HAXPES) was employed for the structural evaluation of ultrananocrystalline diamond/amorphous carbon (UNCD/a-C) composite films deposited on cemented carbide substrates, at substrate temperatures up to 550 °C by coaxial arc plasma deposition. The results were compared with those of soft X-ray photoemission spectroscopy (SXPES). Since nanocrystalline diamond grains are easily destroyed by argon ion bombardment, the structural evaluation of UNCD/a-C films, without the argon ion bombardment, is preferable for precise evaluation. For samples that were preserved in a vacuum box after film preparation, the sp3 fraction estimated from HAXPES is in good agreement with that of SXPES. The substrate temperature dependencies also exhibited good correspondence with that of hardness and Young’s modulus of the films. On the other hand, the sp3 fraction estimated from SXPES for samples that were not preserved in the vacuum box had an apparent deviation from those of HAXPES. Since it is possible for HAXPES to precisely estimate the sp3 fraction without the ion bombardment treatment, HAXPES is a feasible method for UNCD/a-C films, comprising nanocrystalline diamond grains.
Highlights
Nanocrystalline diamond (NCD) films have shown promise as a hard coating material for enhancing the performance of cutting tools and prolonging tool lifetime
The atomic structures of Ultrananocrystalline diamond (UNCD)/amorphous carbon (a-C) composite films were investigated by Hard X-ray photoemission spectroscopy (HAXPES) and soft X-ray photoemission spectroscopy (SXPES)
It was found that the3sp3 fraction estimated from HAXPES spectra corresponds well with the hardness
Summary
Nanocrystalline diamond (NCD) films have shown promise as a hard coating material for enhancing the performance of cutting tools and prolonging tool lifetime. Ultrananocrystalline diamond (UNCD) films, a kind of NCD film comprising grains less than 10 nm [4,5], are a promising candidate as a hard coating application on cutting tools [6]. UNCD films comprise a large number of nano-sized diamond grains, an amorphous carbon matrix [7], and a large number of structurally specific grain boundaries in the films. They are prepared by microwave plasma CVD [8,9] and coaxial arc plasma deposition (CAPD) [10,11,12,13,14]. When prepared with CAPD, we distinctively describe them as UNCD/a-C films
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