Structure and properties of stacking faulted A15 tungsten thin films

A combination of energy-filtered electron diffraction, x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, field-emission scanning electron microscopy, and x-ray diffraction are used to establish that oxygen impurities incorporated in the tungsten films prepared by magnetron sputtering play a dominant role in the formation of the stacking faulted A15 W structure. Energy-filtered electron diffraction data collected from A15 films were Fourier transformed to a reduced density function (RDF), which is compared to theoretical calculations based on several possible structural models. By using a reliability R-factor analysis the A15 W structure has been determined to be a mixed phase consisting of ordered and stacking faulted W₃W structures. The effect of oxygen in stabilizing the stacking faulted A15 structure was also elucidated by in situ anneal and discussed on the basis of structural and thermodynamic stability.