Influence of surfactant Ag on the structure of annealing Ni70Co30/Cu multilayers by X-ray reflection anomalous fine structure and X-ray absorption spectroscopy

We performed X-ray reflection anomalous fine structure and X-ray absorption spectroscopy measurements to investigate the influence of Ag as a surfactant on the annealing Ni70Co30/Cu multilayer for the first time. Interfacial intermixing and silver diffusion levels were quantified at the atomic level. During the deposition, a 6 Å thick intermixing region exists at the Cu/Ni70Co30 interface while the Ni70Co30/Cu interface is sharp for the un-doped and the Ag-doped multilayers. After 285 °C annealing, the two multilayers display different thermal behaviors. Severe diffusion occurs at the Cu/Ni70Co30 and Ni70Co30/Cu interfaces of the un-doped multilayer. However, of these the Ag-doped multilayer do not change significantly, indicating that the addition of silver can suppress interfacial intermixing after annealing. The Ag atoms in the Ag-doped multilayer have diffused into some parts of Ni70Co30 layer while do not exist at the interfaces during the deposition. After 285 °C annealing, the Ag atoms diffused into the whole Ni70Co30 layer as well as some parts of the Cu layer. The X-ray absorption spectroscopy measures show that Ni atoms and Cu atoms occupy the interfacial positions in the un-doped multilayer. The addition of silver also do not change the FCC lattice of Co, Ni and Cu, but decrease the amplitude of the Ni and the Co K edge EXAFS profiles, suggesting that Ag atoms do diffuse into the Ni70Co30 layer.