Interfacial Structure and Mechanical Properties of Compositionally-Modulated Au-Ni thin Films

Abstract

ABSTRACTSeveral characteristics of compositionally-modulated Au-Ni thin films have been observed to vary with composition wavelength for wavelengths between 0.9 and 4.0 nm. The average lattice parameter normal to the film plane displays a maximum, the elastic stiffness shows a minimum and the substrate interaction stress in the film goes through a compressive peak in this regime. These variations are all consistent with a model in which deviations from bulk behavior are confined to the interfaces in the material. In this paper, we present the results of microstructural analyses of these films. Symmetric and asymmetric θ–2θ x-ray diffraction scans were conducted with scattering vectors oriented at a variety of angles to the film normal. Rocking curve analyses were also conducted. Features arising from the composition modulation in symmetric scans are quite sharp. However, asymmetric scans and rocking curves indicate that these films have a relatively poor {111} texture. Data from all scans provide clear evidence that Au intermixes preferentially into Ni. These results are supported by computer simulations of the diffraction spectra and the results of electron-image and -diffraction analyses. These measurements provide a consistent explanation for the mechanical properties of these films.