Self‐Aligned Laser‐Induced Periodic Surface Structures for Large‐Area Controllable Nanopatterning

Abstract

Laser-induced periodic surface structures (LIPSS) have become an important avenue towards surface nanopatterning and certain device applications due to their subwavelength feature size and versatility with different materials. However, the uncontrollable non-uniformity in achievable nanostructures presents a limit towards its practical application. Here, a robust approach is proposed to obtain controllable nanostructures with long-range order based on a new insight into one of the electromagnetic origins of nonuniformity of LIPSS, namely a half-periodic mismatched optical enhancement (h-MOE) effect. The h-MOE effect originates from the interference enhancement of surface plasmon polaritons (SPPs) located between tips of every two adjacent ripples in laser scanning process. It is found that LIPSS can be self-aligned and highly controllable if the h-MOE effect is elaborately modulated through designed laser scanning strategies especially sequential scanning paths. The new laser nanopatterning approach based on h-MOE demonstrates controllable patterning ability to theoretically infinitely large-area super-straight gratings, orientation-controllable gratings, and half-periodic mismatched nanohole arrays.

Self-Aligned Plasmonic Lithography for Maskless Fabrication of Large-Area Long-Range Ordered 2D Nanostructures

“…In addition, the self-aligned phenomenon can also occur on many other semiconductors and metals that can become plasmonically active (whose real part of the permittivity Re(ε) < −1) under ultrafast laser irradiation (with further discussion in S4). 19,35 This approach can support a large number of pattern units initiating simultaneously with one laser pulse irradiation on semiconductors and metals, as SPPs can be excited and interfere homogeneously. 35 The SPL technique can achieve diversified long-range ordered 2D nanostructures under a wide range of processing conditions with gradual morphology evolution, as shown in Figure 2.…”

“…Theoretically, 2D nanopatterns can also be achieved by manipulating the behaviors of SPPs during laser ablation. − Recently, we discovered a novel self-aligned laser ablation phenomenon originating from the interference enhancement of laser-excited SPPs during LIPSS formation named half-periodic mismatched optical enhancement (h-MOE) . This effect allows LIPSS to generate sequentially with an exactly half-periodic mismatched characteristic between adjacent laser scanning paths, namely, in a self-aligned way.…”

“…This morphology evolution can be attributed to the redistributed energy deposition of the scattered field I surf , which comes from the interference between the incident laser and laser-excited SPPs. The scattered field I surf can be approximately obtained by the interference model developed from the dipole radiation model, ,, described as where I 0 is the intensity of the incident laser, σ (Δ d ) is a modulation function related to the depth of the scattering centers Δ d , and F inc and F scat Δ d are the contribution terms from the incident laser and surface scattered waves from the scattering centers (namely, the laser-excited SPPs interference), respectively. Detailed discussions of these terms can be found in eq S12 in section S5 of Supporting Information.…”

“…This robust self-aligned effect also empowers our approach to a self-repair characteristic against local disorder caused by debris or surface contamination, which gradually repairs disorder in the following irradiation (see marked local disorders that gradually disappear in Figure a). Besides, 2D LIPSS can also be morphologically manipulated via tuning the incident laser polarization (Figure S12) and wavelength since the orientation and period of SPPs are highly related to the exciting laser. ,, Moreover, we further fabricate a novel dual-periodic 2D LIPSS (nanohole and nanopillar array shown in Figure S11) by controlling the L of each pulse irradiation and stepwise generating LIPSS.…”

“…32−34 Recently, we discovered a novel self-aligned laser ablation phenomenon originating from the interference enhancement of laser-excited SPPs during LIPSS formation named halfperiodic mismatched optical enhancement (h-MOE). 35 This effect allows LIPSS to generate sequentially with an exactly half-periodic mismatched characteristic between adjacent laser scanning paths, namely, in a self-aligned way. In this work, we further developed a laser 2D nanopatterning technique named self-aligned plasmonic lithography (SPL) by a line-shaped laser based on the above self-aligned laser ablation mechanism.…”