Interface Properties of Al/Ni Multilayers as Deposited and Following Volume Combustion Synthesis

Abstract

ABSTRACTWe report a volume combustion synthesis study of Al/Ni multilayers. The alternating layers of pure Al and pure Ni were grown on silicon and glass substrates using electron beam evaporation. Layers of equal thickness and with bilayer period of 50 nm were grown with total thickness to 1 μm. We focus in this study on the interface properties of as deposited and following anneals up to 660°C with 100°C intervals. Anneal duration was generally 10 min with longer anneals to verify consistency with previously published results. Interface structure was probed using X-ray reflectivity (XRR). Based on interface roughness, we identify three temperature ranges. In the as-deposited to 260°C range the interface properties remain intact, as seen from the XRR interference fringes beyond the critical angle. From 360 to 460°C fringes disappear, indicating the loss of smooth interface morphology. The third temperature range is 500 to 560°C in which the XRR interference fringes are clearly seen, signifying the presence of layering. We describe these results based on a model in which alloy domains form at the interface and grow with temperature and time. Differences in lateral and vertical growth rates of alloy domains are naturally taken into account. At 660°C, the melting temperature of Al, and above the fringes completely vanish. X-ray diffraction is used to identify the nickel aluminide compounds formed upon anneal.