Time resolved x-ray reflectivity study of interfacial reactions in Cu Mg thin films during heat treatment

We present an in-situ time-resolved synchrotron x-ray reflectivity (XRR) analysis of the thermal stability of Cu Mg Cu trilayers during heating ramps up to 300°C at 2°C min. We demonstrate that under some simplifying assumptions the temporal evolution of XRR scans can be used to follow the kinetics of formation of the Cu Mg2 intermetallic phase. The simultaneous refinement of selected parameters of 70 reflectivity scans measured during the heat treatment permits an accurate analysis with respect to the as-deposited state. A gradual damping of the long period Kiessig fringes of the trilayer structure is observed upon heating up to 190°C. Above this temperature the XRR is reminiscent of a single thin film of Cu Mg2. The evolution of interface interdiffusion and/or roughness and thickness of the initial layers allowed to identify a differentiated nucleation and lateral growth process of the intermetallic Cu Mg2 phase depending on the type of interface, Cu on Mg and Mg on Cu. These results are compared to experimental measurements obtained from differential scanning calorimetry. © 2007 The American Physical Society.