The smoothness, hardness and stress in titanium nitride following argon gas cluster ion beam treatment

The surface smoothing of TiN coatings, deposited by CVD or PVD methods, by argon ion clusters comprising a few hundred to a few hundred thousand atoms and carrying a single positive charge has been confirmed. In addition, the present work has shown that there was no change in the mechanical conditio n, nanohardness or residual stress, of the PVD coatings after treatment. In contrast, the nanohardness in the near-surface region of the CVD TIN coati ng was increased but, remarkably, there was no concomitant increase in resi dual stress. A comparison is made with the established effects of classical single ion implantation on the near-surface properties of TiN where a high compressive residual stress is developed if the ion energy lies beyond a t hreshold value. It was concluded that only a fraction of the atoms in the c luster impact the surface and the vast majority of argon atoms move sideway s. It appears to be generic that the smaller clusters are responsible for t he increase in hardness as well as the well-known lateral sputtering effect s associated with the technology. Larger clusters do not carry enough energ y per atom to cause such effects and their energy is dissipated in the subs trate as heat. (C) 2001 Elsevier Science B.V. All rights reserved.