Sputtering of W-Pd bimetallic system under nitrogen plasma impact

Summary form only given, as follows. Summary form only given. In order to optimise the performance of the tungsten-palladium bimetallic system, it is necessary to carry out thorough investigations of its properties under plasma impact, in particular, erosion behavior in hydrogen saturated or non-saturated states. Tungsten protective coatings on a palladium substrate were produced by a vacuum-arc method and by sputtering in a magnetron-type discharge (rodtron configuration) in an argon atmosphere, so that different W-film structures and morphologies were realized. For comparison, virgin samples of pure Pd were also investigated. In our plasma impact studies, the ion energy values were 0.8-16 keV and irradiation doses were 10/sup -18/-10/sup 20/ ions/cm/sup 2/. Erosion coefficient values were measured by a weight loss method. It was shown that the erosion coefficient depends weakly on ion energy for both Pd and W-Pd systems and its value (1.3 at /ion for Pd and 0.2 at /ion for W) is in good agreement with literature data. For hydrogen saturated W-Pd systems, a new kind of radiation damage was observed caused by inhomogeneous adhesion of relatively thick W-films and the changes of sample form from flat to convex. For W-films made by vacuum-arc sputtering, the erosion coefficient value is near to that for bulk tungsten, and does not change to dose about 4.10/sup 19/ ion/cm/sup 2/. For further dose increase, sputtering rate increases up to typical values for bare palladium due to full film disruption. In the case of W-coatings made in a magnetron-type discharge, the erosion coefficient increases monotonically with exposure time. Mechanisms are suggested and discussed to explain such erosion behavior.