Texture development of evaporated nickel films on molybdenum substrates

UHV electron beam evaporation of nickel thin films on molybdenum substrates was carried out at different temperatures between Zone I and low Zone III of the structural zone model. The film texture was studied by energy-dispersive X-ray diffraction and the residual stresses were measured by monochromatic X-ray diffraction, both using the Daresbury synchrotron radiation source. It was found that the nickel film deposited at ambient temperature (Zone I) had a mixed fibre texture with a strong (111) and a weak (002) component. From Zone I-II to Zone II-III, the orientation of the films was dominated by the substrate texture, and granular epitaxy occurred. The films had an imperfect (001)[100] sheet texture, with the (002) and (111) pole figures, respectively, mirroring the (002) and (011) figures of the substrate, which had an imperfect (001)[110] sheet texture. An atomic arrangement model is put forward to explain the pole figure mirroring. The residual stress was found to be tensile and is mainly due to the thermal strain. It is suggested that the minimisation of the free surface energy dominates the texture development of the nickel film at low temperatures, while the anisotropic interfacial energy plays the determining role at elevated temperatures.