Morphological evolution of Au nanowires controlled by Rayleigh instability

Abstract

A sound knowledge and understanding of the thermal stability of nanowires is a prerequisite for the reliable implementation of nanowire-based devices. We investigate the morphology of Au nanowires annealed isothermally at different temperatures. During the processes, triggered by heating, the wires undergo various configurational changes to finally break up into chains of nanospheres at much lower than bulk melting temperatures due to capillary or so-called Rayleigh instability. The role of three parameters, namely, wire diameter, temperature, and annealing time, on the final morphology is investigated. Both the average sphere diameter and the mean spacing between adjacent spheres are larger than the values predicted for materials with isotropic surface energy. Possible reasons are discussed in the paper.

Efficient field emission from structured gold nanowire cathodes

“…In contrast, the NW clusters provide a better mechanical stability and a higher maximum current because of the mutual support and only partial melting of the NW tips. It is most remarkable that many of the cluster-forming NW in figure 9(b) reveal some ripples on their surface which might reflect thermally driven morphological changes much below the bulk melting temperature (Rayleigh instability) [19], thus proving their contribution to the total current of the cluster. With respect to the electrothermal model calculations mentioned above, these melting features indicate a rather large contact resistance between the NW and the substrate.…”

Ultrathin and stable AgAu alloy nanowires

“…The tips of the broken nanowires had spherical shapes because of the reconstruction through the Rayleigh process (Fig. S12) [48]. The variation of local …”

“…Nanowires however can undergo various structural changes at temperatures lower than the estimated melting points for spherical nanoparticles due to the Rayleigh instability [48]. In this case, the driving force for the structural change is the chemical potential gradient (capillarity or surface tension) induced by a perturbation in the radial direction of the nanowires [48].Recently, thin Au nanowires were made by using carbon monoxide at a low flow rate [49]. Unlike the Au nanowires made by using mesophase-template alone, these Au nanowires seem to be stable under e-beam irradiation and no short rods were shown in the TEM micrograph.…”

“…Nanowires however can undergo various structural changes at temperatures lower than the estimated melting points for spherical nanoparticles due to the Rayleigh instability [48]. In this case, the driving force for the structural change is the chemical potential gradient (capillarity or surface tension) induced by a perturbation in the radial direction of the nanowires [48].…”

“…Those ultrathin Au nanowires primarily grew along 111 direction and bounded by {100} facets on the sides when CO gas was not used [33,56]. Au nanowires made under those conditions were unstable and could result in shape transformation into shorter but thicker nanorods due to Rayleigh instability [43,48,52]. In comparison, both Au and AgAu nanowires generated under CO gas were predominately enclosed by {111} surfaces and stable under the e-beam irradiation.…”