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 multila yer thin-films. This mechanism is similar to the sequence that has been pro posed to describe the process of phase formation in several thin-film alumi nide and silicide systems. The data on the formation of NbAl3 from Nb/Al mu ltilayer thin-films are obtained through in situ X-ray diffraction (XRD) ex periments using high-intensity synchrotron radiation. This method permitted the direct detection and observation of the small volume of the product ph ase present at the onset of the reaction. The results are consistent with p revious differential scanning calorimetry (DSC) and microstructural evidenc e provided by cross-sectional transmission electron microscopy (XTEM). (C) 1999 Elsevier Science B.V. All rights reserved.