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Wear, plasticity, and rehybridization in tetrahedral amorphous carbon

: Kunze, T.; Posselt, M.; Gemming, S.; Seifert, G.; Konicek, A.; Carpick, R.; Pastewka, L.; Moseler, M.

Preprint urn:nbn:de:0011-n-2872985 (1.9 MByte PDF)
MD5 Fingerprint: ed79e666412ee1fb723cae5598f3ad9e
Erstellt am: 13.5.2016

Tribology letters 53 (2014), Nr.1, S.119-126
ISSN: 1023-8883
European Commission EC
FP7-PEOPLE; 272619; Topography Evolution
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IWM ()
wear; plasticity; rehybridization; ta-C; tribology; diamond-like carbon; molecular-dynamics simulations; thin-films; deformation; tribochemistry; tribology; mechanism; behavior; failure; growth

Wear in self-mated tetrahedral amorphous carbon (ta-C) films is studied by molecular dynamics and near-edge X-ray absorption fine structure spectroscopy. Both theory and experiment demonstrate the formation of a soft amorphous carbon (a-C) layer with increased sp2 content, which grows faster than an a-C tribolayer found on self-mated diamond sliding under similar conditions. The faster sp3→ sp2 transition in ta-C is explained by easy breaking of prestressed bonds in a finite, nanoscale ta-C region, whereas diamond amorphization occurs at an atomically sharp interface. A detailed analysis of the underlying rehybridization mechanism reveals that the sp3→ sp2 transition is triggered by plasticity in the adjacent a-C. Rehybridization therefore occurs in a region that has not yet experienced plastic yield. The resulting soft a-C tribolayer is interpreted as a precursor to the experimentally observed wear.