Dynamic Recoil Mixing for the Production of Silicon Nitride Films
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DYNAMIC RECOIL MIXING FOR THE PRODUCTION OF SILICON NITRIDE FILMS
H. KHEYRANDISH, J.S. COLLIGON AND A.E. HILL Thin Film and Surface Research Centre, Department of Electronic and Electrical Engineering, University of Salford, Salford M5 4WT, UK ABSTRACT In Dynamic Recoil Mixing (DRM) a film of constant thickness is sputtered on to a substrate by using a broad low energy (lkeV) ion beam and is subsequently bombarded by a high energy (10 key) ion beam. During the bombardment process a dynamic balance is maintained between the backsputtering and the deposition of the film, thus providing an 'unlimited' source of the dopant material. In this way very high surface dopant concentrations may be achieved which otherwise cannot be reached by more conventional ion beam Furthermore, by choosing reactive ion mixing techniques. species, films of novel chemical compositions may be produced. This technique has been employed to produce silicon nitride films on polished commercial mild steel samples. Measurements of knoop hardness of these films indicate an increase of over 200% whilst the wear and friction properties have shown considerable improvement. Conventionally sputtered silicon films of similar thickness, recoil mixed silicon using argon, or implantation of 10 keV argon and nitrogen to similar doses, indicate only a modest change in tribological characteristic compared to the reactive mixed films.
INTRODUCTION In recent years ion implantation has played an important role in altering the hardness, friction and wear of steels and has been the subject of extensive study MI}. An alternative to ion implantation is the deposition of thin films of borides, carbides and nitrides of certain transition metals which are hard and resistant to both wear and corrosion in bulk form. Such films may be produced by reactive sputtering 121, plasma and ion assisted film formation {31, chemical vapour deposition {41 as well as reactive ion beam mixing. In comparison with ion implantation the tribological and corrosion characteristics of such overlayers have been the subject of limited study f5}. It has been established that atomically mixed layers have considerably greater adhesion and endurance {6,71 and the inclusion of silicon in pure iron has been demonstrated to have a significant effect on the oxidation resistance of pure iron {8}. The purpose of the present work has been to investigate the tribological properties of reactive ion beam mixed films of silicon on commercial mild steel.
EXPERIMENTAL The Apparatus The dynamic recoil mixing (DRM) apparatus has been described in detail elsewhere 191 and hence only a brief description of it is presented here. A schematic diagram of this apparatus is shown in Figure 1. It consists of a
Mat. Res. Soc.Symrp.Proc. Vol. 27 (1984) (Elsevier
science Publishing Co., Inc.
514
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Kaufman-type multiray ion source and produces currents of %1 mA/cm of 1 keV There ions and this is used as a sputterine source to deposit thin films. is also a higher energy (10 keV) recoil implanting ion source positioned
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