Solid-state dewetting of Ag/Ni bi-layers: Accelerated void formation by the stress gradient in the bottom Ni layer

• Published in: Journal of alloys and compounds Vol. 960; p. 170735
• Main Authors: Li, Feitao, Flock, Dominik, Wang, Dong, Schaaf, Peter
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2023
• Subjects: Ag/Ni bi-layers; Immiscible; Solid-state dewetting; Stress gradient; Void formation; Ag/Ni bi-layers; Void formation; Solid-state dewetting; Stress gradient; Immiscible
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2023.170735

Solid-state dewetting (SSD) of the immiscible Ag/Ni bi-layers was studied. After annealing at 400 °C for 1 min, the Ag film was dewetted on the Ni film, and this is the first observation about the SSD of one metal film on another metal film. The easier dewetting of Ag than Ni was attributed to its lower melting point, faster grain boundary self-diffusion and poor wettability between them. At 500 °C, the void formation in the bottom Ni layer was highlighted and compared to Ni single layer: many voids in the former while no visible voids in the latter, indicating that the presence of Ag accelerated the SSD of Ni. It was attributed to the vertical stress gradient in the bottom Ni film of Ag/Ni bi-layers, which accelerated the Ni diffusion and formation of the voids in the underlying Ni film around and below the Ag particles. Besides, voids were more easily formed below the Ag particles than between them due to the large lattice mismatch at the Ag/Ni interface and the possible formation of Ag-Ni alloys. The destabilization of the Ag on the Ni film contributes to the understanding of dewetting kinetics, which is beneficial to realize the controllable nanofabrication. [Display omitted] •Solid-state dewetting of Ag film on Ni film after annealing at 400 °C for 1 min.•Voids are formed in Ni film of Ag/Ni bi-layers but absent in pure Ni film at 500 °C.•The weakened stability is due to the vertical stress gradient in the bottom Ni film.•Compressive stress at the Ni/SiO2 interface and tensile stress at the Ag/Ni interface.•The possibility of void formation is higher below the Ag particles than between them.