Novel Self-Organization Mechanism in Ultrathin Liquid Films: Theory and Experiment

Abstract

When an ultrathin metal film of thickness h (<20 nm) is melted by a nanosecond pulsed laser, the film temperature is a nonmonotonic function of h and achieves its maximum at a certain thickness h*. This is a consequence of the h and time dependence of energy absorption and heat flow. Linear stability analysis and nonlinear dynamical simulations that incorporate such intrinsic interfacial thermal gradients predict a characteristic pattern length scale Lambda that decreases for h>h*, in contrast to the classical spinodal dewetting behavior where Lambda increases monotonically as h2. These predictions agree well with experimental observations for Co and Fe films on SiO2.

Nanomaterials synthesis by a novel phenomenon: The nanoscale Rayleigh-Taylor instability

“…[10][11][12] However, while the reliance of intrinsic forces leads to robustness and predictability in pattern formation, such thin film self-organization invariable limits the control over pattern length scale to the form λ ∝ h n , where λ is the self-organized length, h is the film thickness and n varies depending on the conditions used. For instance, in the well studied liquid-phase spinodal dewetting instability, the pattern length scale λ varies with film thickness h as λ ∝ h 211, [13][14][15] and could be modified somewhat by introducing thermal gradients, 16 or by relying on solid state mass transport. 17 While some other ways to overcome this constraint have been demonstrated for polymer liquid films, such as by chemical or morphological modifications to the substrate surface, 18-20 similar flexibility has not been shown for the vast majority of high temperature fluids, such as metals and semiconductors.…”

Coupled self-organization: Thermal interaction between two liquid films undergoing long-wavelength instabilities

“…For comparison, in the semi-analytical method the Fourier transforms of the initial liquid patterns were computed and all Fourier components were evolved independently from each other by using Eq. (21). In this case, the growth or decay of modes is governed by Eq.…”

Instability of nanometric fluid films on a thermally conductive substrate

“…The studies are often carried out using the long-wave approach; within this framework, a significant body of work has been established in the recent years, including extensive research on linear and weakly nonlinear instability mechanisms [4][5][6], as well as discussion of monotone and oscillatory type of Marangoni effect governed instabilities [3,[7][8][9] (only a subset of relevant works is listed here). While most of the works have focused on the regime where gravitational effects are relevant, there is also an increasing body of work considering the interplay between the instabilities caused by Marangoni effect and by liquid-solid interaction that becomes important for the films on nanoscale, see, e.g., [10][11][12][13]. Understanding the influence of Marangoni effect on film stability is simplified in the settings where temperature of the film surface could be related in some simple way to its thickness; however it is not always clear that a simple functional relation can be accurately established, particularly in the setups such that the temperature field and the film thickness evolve on the comparable time scales so that the temperature of the fluid may be history dependent.…”

“…The flow of thermal energy during this short time leads to a complex setup that involves heat flow not only in the metal film but also in the substrate, phase change (both melting and solidification), possible ablation, and chemical effects. Coupling of these effects to fluid dynamical aspects of the problem is just beginning to be understood [12][13][14][15][16].…”