Mechanical and thermal stability of TiN/NbN superlattice thin films

High-temperature stability and mechanical deformation mechanisms of TiN/NbN superlattice structures have been investigated. Single-crystal TiN/NbN sup erlattices were deposited by reactive dual-cathode unbalanced magnetron spu ttering in an Ar/N-2 discharge onto MgO(001) substrates held at a temperatu re of 700 degreesC. The thermal stability was studied by X-ray measurements of superlattice satellite peak intensity variation during and after anneal ing at up to 950 degreesC. The apparent activation energy for metal interdi ffusion in the TiN-NbN diffusion couple is temperature-dependent, with valu es ranging from 2.6 to 4.5 eV. Film hardness as measured by nanoindentation was observed to decrease during annealing, as the result of effective allo ying of the nitride layers. TiN/NbN superlattices are ductile at room tempe rature and exhibit dislocation glide limited to within individual layers in scratching experiments. (C) 2000 Elsevier Science B.V. All rights reserved .