Texture in Ti/Al and Nb/Al multilayer thin films: Role of Cu

Abstract

Fiber texture in Ti/Al and Nb/Al polycrystalline multilayer thin films, with bilayer thicknesses (Λ) ranging from 20–333 nm and having a fixed stoichiometry of 1/3, has been investigated by using x-ray pole figures and transmission electron microscopy. Two sets of films were deposited; one set contained pure Al and the other Al–1.0 wt% Cu. The results indicated that texture was strengthened by the formation of a coherent superlattice for the Nb/pure-Al film with the smallest bilayer thickness. By contrast, the texture in Ti/pure-Al films with a similar period was not as strong. The texture also decreased with increasing Λ for both the Ti/pure-Al and Nb/pure-Al films. An increase in the width of the Al (111) peak and an offset of the fiber axis from the substrate normal of 5–8° was observed in the Λ = 333 nm films prepared by using Al–1.0 wt% Cu. The decrease in texture on addition of Cu to Al was attributed primarily to an increase in interlayer roughness as a consequence of reduction in the Al(Cu) grain size. These observations were interpreted in the context of structure zone and dynamic roughness models of film growth.