Evidence of a two-stage reaction mechanism in sputter deposited Nb/Al multilayer thin-films studied by in situ synchrotron X-ray diffraction

We present new evidence for a two-stage reaction mechanism in Nb/Al multilayer thin-films. This mechanism is similar to the sequence that has been proposed to describe the process of phase formation in several thin-film aluminide and silicide systems. The data on the formation of NbAl3 from Nb/Al multilayer thin-films are obtained through in situ X-ray diffraction (XRD) experiments using high-intensity synchrotron radiation. This method permitted the direct detection and observation of the small volume of the product phase present at the onset of the reaction. The results are consistent with previous differential scanning calorimetry (DSC) and microstructural evidence provided by cross-sectional transmission electron microscopy (XTEM).