Simultaneous Decomposition and Dewetting of Nanoscale Alloys: A Comparison of Experiment and Theory

Abstract

We consider the coupled process of phase separation and dewetting of metal alloys of nanoscale thickness deposited on solid substrates. The experiments involve applying nanosecond laser pulses that melt the Ag 40 Ni 60 alloy films in two setups: either on thin supporting membranes or on bulk substrates. These two setups allow for extracting both temporal and spatial scales on which the considered processes occur. The theoretical model involves a longwave version of the Cahn−Hilliard formulation used to describe spinodal decomposition, coupled with an asymptotically consistent longwave-based description of dewetting that occurs due to destabilizing interactions between the alloy and the substrate, modeled using the disjoining pressure approach. Careful modeling, combined with linear stability analysis and fully nonlinear simulations, leads to results consistent with the experiments. In particular, we find that the two instability mechanisms occur concurrently, with the phase separation occurring faster and on shorter temporal scales. The modeling results show a strong influence of the temperature dependence of relevant material properties, implying that such a dependence is crucial for the understanding of the experimental findings. The agreement between theory and experiment suggests the utility of the proposed theoretical approach in helping to develop further experiments directed toward formation of metallic alloy nanoparticles of desired properties.

Magnetic and Optical Properties of Au–Co Solid Solution and Phase-Separated Thin Films and Nanoparticles

“…While a significant amount of work has been devoted to the dewetting of elemental metal films, recently, the pulsed laser-induced dewetting of miscible 43,47−49 and immiscible metals 34,50−52 has also been studied both experimentally and via molecular dynamics 53 modeling and continuum simulations. 35 Photothermal heating was conducted using a 248 nm KrF excimer laser. Experiments were conducted in a pulsed mode using a 1/e 2 Gaussian pulse width of 18 ns and a top hat spatial distribution.…”

“…A 40 nm thick low-stress SiN x membrane (≈150 μm × ≈150 μm) supported by a 300 μm thick Si frame was used. The previous work on 10 nm thick Ag 60 Ni 40 thin films provides approximate heating conditions required to generate nanoparticles on both substrates and suggests a liquid lifetime of approximately 20 ns for dewetting. Finite element thermal simulations shown in Figure j indicate that a fluence of ≈140 mJ/cm 2 provides a sufficient liquid lifetime for the SiO 2 -coated Si bulk substrates, while only ≈40 mJ/cm 2 is necessary for the thin transparent substrates.…”

Sessile drop evaporation in a gap -- crossover between diffusion-limited and phase transition-limited regime

“…For systems with more degrees of freedom, the described one-field model (2.1) is extended by incorporating the dynamics of further fields (Thiele 2018). In the context of thin-film hydrodynamics, two-field gradient dynamics models are presented and analysed for (i) dewetting two-layer films on solid substrates, i.e., staggered layers of two immiscible fluids (Pototsky et al 2004(Pototsky et al , 2005Jachalski et al 2013;Bommer et al 2013), (ii) decomposing and dewetting films of a binary liquid mixture (with non-surface active components) (Thiele 2011;Thiele et al 2013;Diez et al 2021), (iii) the dynamics of a liquid film that is covered by an insoluble surfactant (Thiele et al 2012(Thiele et al , 2016, (iv) the spreading of a liquid drop on a polymer brush (Thiele & Hartmann 2020) and (v) on an elastic substrate without (Henkel et al 2021) and with (Henkel et al 2022) Shuttleworth effect. In all these cases, the model is of the form…”

Liquid film rupture beyond the thin-film equation: a multi-component lattice Boltzmann study

“…Several experimental works studied the evolution of thin films on horizontal partially-wettable surfaces [23][24][25][26], chemically structured walls [27], films with toroidal shape [28] or surrounded by a second viscous phase [29]. Pulsed-laser-induced dewetting of metal alloys has also been investigated [30][31][32][33][34]. The most popular model to describe dewetting phenomena is the celebrated TFE [12], which describes the spacetime evolution of the film height profile h(x, t).…”