Pressure influence on the depth resolution of rf-glow discharge depth profiling of multilayer coatings

Abstract

Multilayer coatings (MLC) of known composition and thickness, 5×(100 nm Al/100 nm Ti), 10×(300 nm CrN/300 nm CrAlN)/100 nm Cr and 30×(100 nm CrN/100 nm CrAlN)/100 nm Cr, deposited onto steel substrates (SS) were analysed by depth profiling using radiofrequency (rf)-glow discharge optical emission spectroscopy (GD-OES). The aim of the investigation was to find the optimal depth resolution by varying the rf-powered discharge guiding parameters. For the samples analysed here, the selected rf-discharge guiding parameters were the peak-to-peak voltage and the argon flow rate. Optimal discharge conditions were obtained by applying a constant peak-to-peak voltage of 2000 V as well as low Ar flow rates [40–50 standard cubic centimetres per minute (sccm)], where the relative depth resolution of the MLC/SS interface region improved significantly. A transient unstable rf-discharge pressure regime resulting in a worse depth resolution was also found.