Comparative study of thin film physical properties for TiNx deposited by DC magnetron sputtering under temperatures less than 100 degrees C on monocrystalline silicon and polycrystalline iron substrates

In this research, titanium nitride thin films were deposited by reactive DC magnetron sputtering with two original constraints imposed by the expected industrial application as roll to roll decorative coating of steel: the sa mples should be connected to earth and should not be heated during depositi on. Previous work has shown that low N-2 atmospheres should be maintained d uring sputtering processes in order to obtain a colour range from grey to g old, In this study, the nitrogen content measured by Resonant Nuclear React ion Analysis and the crystal structure revealed by glancing angle X-ray dif fraction, were used to determine the coating composition. The appearance pr esented in CIE L*a*b* colour coordinates and the micro-hardness obtained wi th a Berkovitch nano-indenter were also evaluated for all the films. Result s obtained with the TiNx layers deposited on monocrystalline polished silic on were then compared to coating physical properties measured on polycrysta lline iron (alpha-Fe) substrates. Only the coating produced under the lowes t N-2 gas flow exhibits a different nitrogen content on both substrates res ulting in an hexagonal phase on iron. Colour differences appear and are pro bably due to different substrate roughness. Hardnesses between 12 and 22 GP a are obtained on both substrates. Such results tend to qualify this proces s for possible industrial application as a protective coating with a pleasa nt appearance. (C) 1999 Elsevier Science S.A. All rights reserved.