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Microtribological behaviour of thin DLC films using different testing methods

Mikrotribologisches Verhalten von dünnen DLC-Schichten mit unterschiedlichen Prüfverfahren
: Bandorf, R.; Lüthje, H.; Staedler, T.


TriboTest 12 (2006), Nr.2, S.113-118
ISSN: 1354-4063
Fraunhofer IST ()
Tribologie; Reibung; Verschleiß; Verschleißprüfung; Prüfverfahren; Vergleichsmessung; Mikroelektronik; diamantähnlicher Kohlenstoff; Aufdampfschicht; Mikrosystemtechnik; Rasterkraftmikroskopie; Reibungskoeffizient

To enhance the lifetime and reliability of microcomponents, thin microtribological films are applied to microparts. With reduction of the component size, investigation methods for tribological testing must be adapted. This paper studies the microtribological behaviour of thin diamond-like carbon (DLC) films using different testing methods. To tie in with macroscopic results, to determine friction we used the well-known pin-on-disc test with spherical surfaces of 10mm diameter under a typical load of 3N. For investigations of the behaviour under single asperity contact, Atomic Force Microscope (AFM) methods with applied loads of a few hundred micronewtons were used. Investigations on thin DLC films showed that the friction coefficient under single asperity contact is strongly dependent on the applied load and the resulting contact area. Especially for thin films (up to a few hundred nanometres) the friction coefficient is influenced by the substrate material. With decreasing substrate Young's modulus the friction coefficient also decreases. On the other hand, an increase in the abrasive wear resistance was observed using soft substrate materials. In this paper we show that the friction coefficient was also reduced by a simple surface structure. For investigations we used photolithography to create concentric circles in different substrates. This resulted in a behaviour like riding on rails for the pin-on-disc test. Depending on the tribological pairing the friction coefficient was reduced to more than 50% of the original value.