Microstructure and growth modes of stoichiometric NiAl and Ni3Al thin films deposited by r.f.-magnetron sputtering

Intermetallic thin films of stoichiometric NiAl and Ni3Al have been deposited onto n-type silicon (100) and nickel (110) substrates using r.f.-magnetron co-sputtering. The morphology and crystal structure of the thin films have been studied by transmission electron microscopy from planar-view and cross-sectional samples. Chemical order has been assessed using nano-diffraction techniques. Superlattice reflections confirm a fully ordered structure in both intermetallics. These NiAl and Ni3Al thin films are nanoscaled with an average grain size ranging from 50 to 100 nm and exhibit fiber textures in the (110) and (111)directions when deposited onto silicon. Granular- and heteroepitaxial relations have been observed when sputtering onto nickel at high substrate temperature. A granular-heteroepitaxial mode of growth exhibiting the inverse Nishiyama-Wassermann relation (211)[211](B2) \\ (110)[110](fcc) is observed in NiAl for the first time, whereas a single-crystalline heteroepitaxial growth relation of (110)[110](LI2) \\ (110)[110](fcc) is achieved in Ni3Al. The interface chemistry and surface topography have been studied by secondary ion mass spectroscopy and scanning tunneling microscopy, respectively, indicating an oxygen-free layer of very low surface roughness. The influence of the lattice matching and the deposition parameters on the thin film microstructure and orientation are discussed. (C) 2000 Elsevier Science S.A. All rights reserved.