Friction and wear of argon-implanted silicon crystals
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N. Preikschas and B. Cleff Institute of Nuclear Physics, Munster, Germany
M. Cholewaa) and G. J. F. Legge Micro Analytical Research Centre, School of Physics, The University of Melbourne, Australia (Received 15 July 1993; accepted 3 August 1993)
Silicon (111) single crystals were implanted with 70 keV Ar ions to the dose of 1017 ions/cm 2 . Next, the friction coefficient between a Si crystal and a hard steel ball was measured using a pin-on-disk setup in air and in vacuum. The wear tracks were measured using a surface profilometer. For measurements performed in vacuum, a strong influence of implantation on friction force and wear tracks was found. The microstructure of the samples was subsequently investigated using RBS, ERD, and x-ray diffraction (XRD) techniques. Micro-RBS measurements showed that Ar had been removed from the wear tracks, despite their continued exhibition of low friction.
I. INTRODUCTION Ion implantation in tribology has already over 20 years of history.1 Its advantages are well known: precise control of the total number of injected ions, control of the depth of penetration, unrestricted choice of an implanted ion-target combination, possible concentrations of implanted species above the solid solubility limit, possible implantation at different temperatures, etc. As results, many researchers report changes in friction coefficient and microhardness or improved wear behavior, increased adhesion of thin films to the substrate or improved corrosion resistivity. Materials investigated so far include metals, with particular emphasis on steels, plastics, carbides, and ceramics.2'3 Significant research has been done in technologically important fields. Results are not easy to interpret and explain because of the great complexity of investigated physical systems and the many factors influencing tribological systems: morphological, physical, and chemical. In our experiments, in order to simplify the investigated system, silicon single crystals were chosen. Such a system has no direct technical importance; however, it should be mentioned that generally mechanical properties of metal-semiconductor systems are not far from applications.4 II. EXPERIMENTAL Silicon (111) samples were cut from industrial standard, Czochralski-grown rods (5 cm diameter) and polished using 2.5 yu-m aluminum oxide powder. Samples a) Author
on leave from the Institute of Nuclear Physics, Cracow,
Poland. J. Mater. Res., Vol. 9, No. 1, Jan 1994
http://journals.cambridge.org
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were then cleaned with acetone and methanol in an ultrasonic cleaner and glued to metal holders. Next, several samples were implanted in the mass separator facility of the Institute of Nuclear Physics in Cracow with argon ions of energy 70 keV up to the dose of 1017 ions/cm 2 . Argon was chosen to avoid chemical effects associated with implanted ions. The implantation dose was high enough to ensure the total amorphization of the surface layer. Friction coefficients of all samples against a steel ball were measured using a standard p
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