Cross-sectional characterization of the dewetting of a Au/Ni bilayer film

Abstract

The solid state dewetting of Au/Ni bilayer films was investigated by cross-sectional transmission electron microscopy techniques, including energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy and precession electron diffraction. After annealing under high vacuum conditions the early stage of film agglomeration revealed significant changes in film morphology and chemical distribution. Both Au and Ni showed texturing. Despite the initial deposition sequence of the as-deposited Au/Ni/SiO/Si interface structure, the majority of the metal/SiO interface was Au/SiO after annealing at 675°C for 1h. Void nucleation was predominantly observed at Au/Ni/SiO triple junctions, rather than grain boundary grooving at free surface of the metal film. Detailed cross-sectional characterization reveals that the Au/Ni interface in addition to small amounts of metal alloying strongly affects film break-up and agglomeration kinetics. The formation of Au/SiO interface sections is found to be energetically preferred over Ni/SiO due to compressive stress in the as-deposited Ni layer. Void nucleation is observed at the film/substrate interface, while the formation of voids at Ni/Au phase boundaries inside the metal film is caused by the Kirkendall effect.

Agglomeration and long-range edge retraction for Au/Ni bilayer films during thermal annealing

“…Generally, polycrystalline thin filmsare assumed to dewet homogenously because of local capillary driven grain boundary grooving [15].In this study, however, film agglomeration occurs homogeneously only in the center of the substrate waver, i.e., in region P1, while long-range edge retraction is nucleated by local defect structures with convex geometry [34], and interface energy. The latter observation is consistent with cross-sectional TEM characterization previously carried out in region P1 [35].…”

Modeling solid-state dewetting of a single-crystal binary alloy thin films

“…(6) and (7)) is due to wetting/dewetting effect [31][32][33], which is stated next in Eqs. (8), (9) and (10).…”

“…[26] after the map onto a planar geometry and the application of SSA, and using a more convenient and standardized notations. Equations (9) and (10) [26], where the right-hand sides are certain functions of the surface orientation angle θ; this, and the inclusion of the anisotropy terms in the chemical potentials µ A and µ B introduce the anisotropy into the model of Ref. [26].…”

Laser-induced metastable mixed phase of AuNi nanoparticles: a coherent X-ray diffraction imaging study

“…The dark Ni-rich area in the SEM image is larger than the corresponding area in the CXDI image. Considering that the SEM image is surface sensitive while the CXDI image represents a projected density profile, we conjecture that the Ni-rich region is segregated in the top part of the particle underneath which Au exists (Nguyen et al, 1993;Lambrecht et al, 1987;Cen et al, 2017).…”

“…3 corresponds to the Au-rich phase, while the valley near 180 nm represents the Ni-rich region. The peak near 220 nm consists of the Ni-rich surface region, underneath which lies the Au-rich region that might have penetrated into the Si 3 N 4 substrate (Nguyen et al, 1993;Lambrecht et al, 1987;Cen et al, 2017). The line profiles of the last two images (50 and 250 accumulated laser shots) indicate that the phase boundary disappears and that the sample transforms to a nonequilibrium mixed state.…”