λ/20 surface nanostructuring of ZnO by mask-less ultrafast laser processing
Shi Bai1,2, Zhaoxu Li2, Kotaro Obata1
1Advanced Laser Processing Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Nanophotonics (Berlin, Germany)
|December 5, 2024
Summary
Ultrafast laser processing fabricates ZnO nanostructures like nanostrips and nanopillars, enabling enhanced surface-enhanced Raman scattering (SERS) applications with a high enhancement factor.
Area of Science:
- Materials Science
- Nanotechnology
- Optics
Background:
- Fabricating nanostructures below the optical diffraction limit is challenging.
- Laser-induced periodic surface structures (LIPSS) are formed by polarized ultrafast laser irradiation.
- LIPSS offer potential in photonic applications like surface-enhanced Raman scattering (SERS).
Purpose of the Study:
- Investigate the morphologies of LIPSS on ZnO substrates using mask-less ultrafast laser processing.
- Explore the influence of laser parameters on nanostructure formation.
- Evaluate the SERS performance of fabricated ZnO nanostructures.
Main Methods:
- Mask-less ultrafast laser processing of ZnO substrates.
- Controlled adjustment of laser parameters: fluence, pulse number, polarization, and pulse duration.
- Coating gold nanoparticles on ZnO nanopillar arrays for SERS.
Main Results:
- Homogenous nanostrip and nanopillar arrays were successfully created on ZnO.
- Individual nanogrooves (∼20 nm width) and nanocavities (∼24 nm diameter) were fabricated by tuning laser fluence.
- Laser irradiation increased defect concentration in ZnO, enhancing SERS performance.
Conclusions:
- Ultrafast laser processing is effective for fabricating diverse ZnO nanostructures.
- The created ZnO nanostructures, particularly nanopillars with gold nanoparticles, exhibit excellent SERS capabilities.
- Achieved a significant SERS enhancement factor of 2.28 × 107, demonstrating the potential for sensitive detection.
