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 el ectron microscopy, and x-ray diffraction are used to establish that oxygen impurities incorporated in the tungsten films prepared by magnetron sputter ing play a dominant role in the formation of the stacking faulted A15 W str ucture. Energy-filtered electron diffraction data collected from A15 films were Fourier transformed to a reduced density function (RDF), which is comp ared to theoretical calculations based on several possible structural model s. By using a reliability R-factor analysis the A15 W structure has been de termined to be a mixed phase consisting of ordered and stacking faulted W3W structures. The effect of oxygen in stabilizing the stacking faulted A15 s tructure was also elucidated by in situ anneal and discussed on the basis o f structural and thermodynamic stability. (C) 2001 Kluwer Academic Publishe rs.