Solid-State Dewetting of Thin Films

Abstract

Solid films are usually metastable or unstable in the as-deposited state, and they will dewet or agglomerate to form islands when heated to sufficiently high temperatures. This process is driven by surface energy minimization and can occur via surface diffusion well below a film's melting temperature, especially when the film is very thin. Dewetting during processing of films for use in micro- and nanosystems is often undesirable, and means of avoiding dewetting are important in this context. However, dewetting can also be useful in making arrays of nanoscale particles for electronic and photonic devices and for catalyzing growth of nanotubes and nanowires. Templating of dewetting using patterned surface topography or prepatterning of films can be used to create ordered arrays of particles and complex patterns of partially dewetted structures. Studies of dewetting can also provide fundamental new insight into the effects of surface energy anisotropy and facets on shape evolution.

Efficient Photocatalytic H2 Evolution: Controlled Dewetting–Dealloying to Fabricate Site‐Selective High‐Activity Nanoporous Au Particles on Highly Ordered TiO2 Nanotube Arrays

“…[12,15,17] In order to investigate the influence of the Au loading, we fixed the Ag/Au ratio to 2:1 ( Figure 4(b)), and deposited various thicknesses of the metal layers -in line with theory on dewetting mechanisms, the thickness of the metal layer, i.e., the amount, strongly influences dimension and distribution of the dewetted particles (see Figure S4 and ESI for more details). [18] For the configurations (and loadings) where mixed ground/crown or a full ground position was established, a clearly lower H 2 evolution efficiency was obtained compared to only crown position. To shed more light on this aspect, we fabricated sample "5*" by sputtering a (nominally) 5 nm thick Au layer placing the tube arrays in a special configuration, that is, the tube layer was placed parallel to the direction of sputtering, in order to deposit the metal (Au/Ag) film only on crown position.…”

“…The occurrence of thermal dewetting is commonly attributed to the tendency of the metal film to minimize its surface energy on a non-wetting substrate, and consequently to break up forming agglomerates. [18] The morphology of the dewetted particles is strongly influenced by different parameters, which are precisely the metal film thickness, the film homogeneity, the dewetting atmosphere, the substrate morphology and its chemical nature. [12,15,[17][18][19][20][21][22][23][24][25] In general, the locations at which a thin metal film brake up (i.e., "hole formation") are random, but this process can be site-controlled by adopting regularly patterned substrate topographies.…”

Self-assembled antireflection coatings for light trapping based on SiGe random metasurfaces

“…One viable and promising route is solid-state dewetting of ultra-thin films of metals 18,[34][35][36][37][38][39][40][41] and semiconductors, [42][43][44][45][46] a natural phenomenon exploited for the self-assembly of high-quality photonic structures. The instability giving rise to the dewetting phenomenon in thin films is mediated by the surface diffusion of atoms and occurs upon annealing at high temperature (even well below the melting point of the material) [47][48][49][50][51][52][53][54][55][56][57][58] . Arrays of well separated islands, featuring a random spatial organization and a relatively large spread of sizes and shapes can be produces.…”

Annealing of Au, Ag and Au–Ag alloy nanoparticle arrays on GaAs (100) and (111)B

“…The main research focus on annealing effects has been devoted to NP formation during so-called thin film annealing [21][22][23][24][25][26].…”