Surface and Coatings Technology 157 (2002) 138–143 0257-8972/02/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0257-8972 Ž 02 . 00146-9 Structure and composition of Ti Al N thin films sputter deposited using x 1yx a composite metallic target J.Y. Rauch , C. Rousselot , N. Martin * a b c, Metatherm S.A., 18, Rue de la Craye, F-25150 Vermondans, France a ´ CREST UMR CNRS, 4, Place Lucien Tharradin, F-25211 Montbeliard, France b ´ ENSMM—Laboratoire de Microanalyse des Surfaces, 26, Chemin de l’epitaphe, F-25030 Besancon Cedex, France c ¸ ´ Received 23 September 2001; accepted in revised form 22 March 2002 Abstract An original composite target configuration with various S y(S qS ) area ratios was used to prepare hard Ti Al N thin Ti Ti Al x 1yx films by r.f. reactive magnetron sputtering. The crystallographic structure of the films deposited on high-speed steel and glass substrates was determined by X-ray diffraction. Homogeneity was investigated from compositions and depth profile measurements carried out by Rutherford backscattering spectroscopy, electron probe microanalysis and glow discharge optical emission spectroscopy. The modulation of the Ti and Al area ratios of the target produced changes of the structure from the fcc TiN to the hexagonal AlN phase and simultaneously, a gradual modification of the Ti Al N metal concentration from xs0 to 1. The x 1yx mechanical behaviours such as hardness and scratch tests were also determined and correlated with the evolution of the structural and compositional properties.  2002 Elsevier Science B.V. All rights reserved. Keywords: TiAlN films; Reactive sputtering; Composite target 1. Introduction Titanium nitride thin films have been especially attrac- tive because of their high hardness characteristic, good wear resistance, mechanical and optical properties w1– 4x. One of the main disadvantages of the TiN compound in some applications is that it oxidises easily in air at above 700 K giving rise to a TiO component, which 2 contributes to the degradation of its wear resistance w5x. In recent years, (Ti,Al)N films have drawn much atten- tion since the addition of aluminium to TiN to form a ternary solid solution enhances the anti-oxidation behav- iours and improves the cutting performance in compar- ison to that of TiN w6–8x. There has been a great number of papers devoted to the properties of (Ti,Al)N alloy films deposited by chemical vapour deposition w9x, by ion plating w10x or by reactive sputtering w11–13x. Several approaches have been used to deposit (Ti,Al)N coatings by reactive sputtering with various Ti and Al *Corresponding author. Tel.: q33-381-40-28-79; fax: q33-381- 40-28-52. E-mail address: nicolas.martin@ens2m.fr (N. Martin). target compositions. A Ti target with Al inserts (or inversely), two opposing elemental targets of Ti and Al or a composite target with variable Ti yAl surface areas w14–16x. In this paper, attention is focused on Ti Al N thin x 1yx films prepared by r.f. reactive magnetron sputtering from a composite Ti yAl target. An original target configura- tion winterchangeable of the S y(S qS ) area ratiosx Ti Ti Al is used to vary the amount of sputtered Ti and Al. An increase of the S y(S qS ) area ratio of the target Ti Ti Al systematically leads to homogeneous Ti Al N com- x 1yx pounds with a stoichiometric nitrogen concentration but with a Ti-deficient composition wTi-deficient means x value lower than the corresponding S y(S qS ) area Ti Ti Al ratiox. A simple theoretical approach allows to predict the composition of Ti Al N thin films. The variations x 1yx of the Ti and Al contents in the films also result in modifications of the crystallographic structure and mechanical properties. 2. Experimental Ti Al N thin films were prepared by r.f. reactive x 1yx magnetron sputtering in a high vacuum reactor (SCM