Multilayer structure, stress reduction and annealing of carbon film
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Multilayer structure, stress reduction and annealing of carbon film. Peter C.T. Ha 1, D.R. McKenzie 1, D. Doyle 2, D.G. McCulloch 3, Richard Wuhrer 4, 1
School of Physics, University of Sydney, Sydney, NSW, 2006. Australia Sutton Tools, Thomastown, Melbourne, 3758. Australia 3 Department of Applied Physics, RMIT, Melbourne, 3001. Australia 4 Microstructural Analysis Unit, University of Technology, Sydney, 2007. Australia. 2
ABSTRACT: Carbon films deposited by filtered cathodic arc show a high compressive stress which limits their thickness because of delamination. We study three methods of relieving the stress in these films. We first determine the dependence of the stress on DC bias up to bias voltages of 1200V and show that the formula of Davis provides a good fit to the data including the stress maximum in the region of 150-200V and the progressive decrease in stress at higher voltages. In the second method, plasma immersion ion implantation (PIII) was used to create multilayer of alternating high density, high stress (PIII on) films and lower density, low stress (PIII off) films. This method enabled thicker structures to be produced. In the third method we made multilayers using amorphous silicon and carbon layers. Annealing of these layers showed that the stress could be reduced to very low values because of the ability of the silicon layers to absorb compressive stress by contracting after the annealing step. The microstructural effects of PIII were studied by transmission and scanning electron microscopy. INTRODUCTION Recently, there has been a considerable interest in multilayer films for wear resistance and tribological applications [1,2,3,4,5]. Multilayer films consisting of sequential layers of two different materials have been reported as having under some conditions, a higher value of fracture toughness [6] and a high value of elastic modulus [4] than single layer films of either constituent [3]. The fracture toughness of a multilayer structure can be optimized by correct choice of each layer thickness [7]. As for thin film coating, the adhesion of a single or multilayer film to the substrate is strongly affected by the intrinsic stress in the coatings. Pulse biasing of the substrate during deposition leads to a variation of the ion energy that when implanted, the carbon ions can penetrate the substrate resulting in complete interfacial mixing [8]. Diamond-like carbon coatings have been used as solid lubricating coatings because of their low friction and good wear resistance properties. The filtered cathodic vacuum arc (FCVA) technique is an effective method for producing high quality coatings, but has limitations for preparing thick hard carbon coatings, especially tetrahedral amorphous carbon (ta-C) films because of high compressive stress. Multilayer structures have been proposed as a way to overcome this limitation [5,9]. In this paper, we investigate three methods of stress reduction in ta-C films using multilayer structures. In the first method, we used pulsed bias (PIII) and create mul
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