Anisotropic Nanoscale Wrinkling in Solid‐State Substrates

Abstract

Pattern formation induced by wrinkling is a very common phenomenon exhibited in soft-matter substrates. In all these systems, wrinkles develop in the presence of compressively stressed thin films lying on compliant substrates. Here, the controlled growth of self-organized nanopatterns exploiting a wrinkling instability on a solid-state substrate is demonstrated. Soda-lime glasses are modified in the surface layers by a defocused ion beam, which triggers the formation of a compressively stressed surface layer deprived of alkali ions. When the substrate is heated up near its glass transition temperature, the wrinkling instability boosts the growth rate of the pattern by about two orders of magnitude. High-aspect-ratio anisotropic ripples bound by faceted ridges are thus formed, which represent an optimal template for guiding the growth of large-area arrays of functional nanostructures. The engineering over large square centimeter areas of quasi-1D arrays of Au nanostripe dimers endowed with tunable plasmonic response, strong optical dichroism, and high electrical conductivity is demonstrated. These peculiar functionalities allow these large-area substrates to be exploited as active metamaterials in nanophotonics, biosensing, and optoelectronics.

Self-Organized Nanorod Arrays for Large-Area Surface-Enhanced Infrared Absorption

“…Anisotropic nanoscale wrinkles extending over large cm 2 areas are induced on the surface of commercial microscope glass slides by self-organized nanopatterning. [ 49 ] The ion-induced wrinkling instability in amorphous substrates is here exploited (see the Methods section) for driving the growth of ordered arrays of high aspect ratio nanowrinkles bound by faceted ridges as long as several micrometers, as shown by the atomic force microscopy (AFM) image in Figure 1a.…”

“…After the high ion fluencies amounting to 1.4 × 10 19 ions/cm 2 , the ion-driven wrinkling instability enables the growth of nanostructures as high as 100 nm with a periodicity of about 250 nm ( Figure 1b), which are characterized by an asymmetric faceted profile (typical slopes of the two ripple ridges of 30 and 50°, respectively). [ 49 ] The highly ordered faceted templates allow us to easily confine quasi-1D arrays of tilted noble metal nanostripes by a single-step maskless process based on kinetically controlled noble metal evaporation at a glancing angle. The scanning electron microscopy (SEM) image of Figure 1c shows the example of Au nanostripe arrays confined on the steeper ripple ridges (50−60° with respect to the sample plane).…”

Large-area flexible nanostripe electrodes featuring plasmon hybridization engineering

“…2(d). A similar approach was previously followed in the case of self-organised faceted glass templates prepared by ion beam sputtering [9,47,48] which highlighted the possibility to fabricate plasmonic arrays with a broadband response determined by inhomogeneous broadening i.e., by the incoherent superposition of the plasmonic response of Au nanoparticles with an intrinsically broad size line profiles show the increase of period when the laser incidence angle  is modified from 45°, to 40° and 35°. The projection of the Au atomic beam at grazing angles highlights the shadowing mechanism exploited to synthesize tilted Au NSs.…”

Self-Organized Conductive Gratings of Au Nanostripe Dimers Enable Tunable Plasmonic Activity

“…Periodic quasi-1D nanoripples as long as several micrometers and characterized by a mean height of about 80 nm are shown in Figure 1a,b (AFM topography and cross section profile). The rippling mechanism drives the peculiar growth of facets at the amorphous surface, which are asymmetrically tilted out of plane [30,32], as sketched by the in-scale cross-section profiles of Figure 1d,e. In particular, the ridges directly exposed to the ion beam irradiation exhibit typical slopes of α exceeding 50 • , while the opposite show highly defined orientation at about 30 • (Supporting Information, Figure S1).…”

“…On the other hand, self-assembled nanofabrication methods [27][28][29] allow the large-area functionalization of surfaces, but are generally characterized by low homogeneity and the limited possibility of tailoring the nanostructure's shape.Here, large-area (cm 2 ) highly ordered plasmonic templates are prepared by a novel maskless self-organized nanofabrication method. A nanoscale wrinkling instability in glasses induces quasi-1D nanopatterned templates, which enable the confinement of out-of-plane tilted plasmonic nanostripes and/or nanostripe dimers [30]. The method allows the easy tailoring of the nanostripes' morphology, and thus the tuning of their localized plasmon resonances across the visible (VIS) and near-infrared (IR) spectrum.…”