Mechanical Deformation–Assisted Fabrication of Plasmonic Nanobowties with Broken Symmetry and Tunable Gaps

Abstract

A symmetry broken and gap tunable gold nanobowtie array is demonstrated by nanosphere lithography performed on a mechanically uniaxially prestretched elastomeric substrate. Due to symmetry breaking of each nanotriangle with its three neighboring nanotriangles once the uniaxial prestretch is released, the structure exhibits polarization‐dependent optical properties. In addition, the decrease in the gap between adjacent triangles provided by mechanical relaxation of the substrate enhances the electric field enhancement between adjacent triangles, which in turn results in enhanced Raman scattering from molecules present in the gap. Triangle apex‐to‐apex gaps as small as 20 nm are generated using a colloidal crystal formed from 500 nm colloids on at 30% prestretched substrate (gaps formed when an unstretched substrate is used are ≈115 nm).

Mechanically Tunable Nanogap Antennas: Single‐Structure Effects and Multi‐Structure Applications

“…using nanosphere lithography to fabricate triangles on a pre‐stretched PDMS substrate. [ 104 ] A monolayer of polystyrene (PS) beads was deposited on pre‐stretched PDMS (0%, 10%, 20%, 30%), and 5 nm chromium and 50 nm gold were deposited. After removing the PS bead mask, the PDMS was relaxed, which resulted in the adjacent triangles moving closer together, forming bow tie antennas from two triangles with gaps down to 20 nm.…”

Photoelastic plasmonic metasurfaces with ultra-large near infrared spectral tuning

“…Mechanical deformation can directly reform the lattice periodicity of the meta-atoms, and is hence deemed as an efficient approach for active metasurfaces for spectrum tuning [32] , structural colors [33] , varifocusing [34] , dynamic holography [35] , and so on. Several metasurfaces fabricated on soft substrates exhibit spectral tuning upon externally applied strain through mechanical stretching [33,36,37] . To exclude the cumbrous physical contact for obtaining the deformation and to miniaturize the system size for further optoelectronic integration, active metasurfaces possessing mechanical deformability that can be controlled with remote stimuli would be strongly desired.…”

“…Several metasurfaces fabricated on soft substrates exhibit spectral tuning upon externally applied strain through mechanical stretching. 33,36,37 To exclude the cumbrous physical contact for obtaining the deformation and to miniaturize the system size for further optoelectronic integration, active metasurfaces possessing mechanical deformability that can be controlled with remote stimuli would be strongly desired.…”

Hexagonal arrays of plasmonic gold nanopyramids on flexible substrates for surface-enhanced Raman scattering

“…Their plasmonic coupling increases, thus enhancing the local electromagnetic field [31]. Strain sensitive experiments with bowtie nanoantennae on PDMS allowed for further LSP investigations [26,32,33].…”