Correlation between fracture characteristics and valence electron concentration of sputtered Hf-C-N based thin films

• Hard protective coating materials based on transition metal nitrides and carbides typically suffer from limited fracture tolerance. To further tune these properties non-metal alloying - substituting C with N - has been proven favorable for magnetron sputtered Hf-C-N based thin films. A theoretically predicted increase in valence electron concentration (from 8.0 to 9.0 e/f.u. from Hf-C to Hf-N) through nitrogen alloying lead to an increase in fracture toughness (K-IC obtained during in-situ SEM cantilever bending) from 1.89 +/- 0.15 to 2.33 +/- 0.18 MPa.m(1/2) for Hf0.43C0.57 to Hf0.35C0.30N0.35, respectively. The hardness remains close to the super-hard regime with values of 37.8 +/- 2.1 to 39.9 +/- 2.7 GPa for these specific compositions. Already the addition of small amounts of nitrogen, while sputtering a ceramic Hf-C target, leads to a drastic increase of nitrogen on the non-metallic sublattice for fcc single phased structured HfC1-xNx films, where x = N/(C + N). The here obtained results also provide experimental proof for the correlation between fracture characteristics and valence electron concentration.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Nyckelord

Hf-C-N

Fracture resistance

Non-metal alloying

Valence electron concentration

Thermal stability

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