Asymmetric diffusion as a key mechanism in Ni/Al energetic multilayer processing: A first principles study

Adsorption and penetration of Al and Ni atoms into Ni(111) and Al(111), respectively, are investigated through first principles calculations, shedding light into the driving forces impacting Al/Ni interfaces produced during multilayer deposition. The authors show that Ni deposition follows an exothermic path toward penetration associated with small activation barriers while Al on Ni(111) path is endothermic accompanied with high activations. Moreover, Ni and Al penetrations proceed through interstitial and substitutional sites, respectively. These differentiated behaviors at early deposition stages illustrate that dual processing conditions are required to achieve the growth of specific Ni/Al interfaces during multilayer deposition processes and that a local melting process at the interface is mandatory to arrive at the formation of a proper barrier layer.