Site-Controlled Preparation of Au Micro/Nanostructures Toward Enhancing Raman Scattering

As a sensing method with single molecule-level resolution in theory, surface-enhanced Raman scattering (SERS) shows robust applications in wide fields. However, due to technical limitations, it remains challenging to obtain effective plasmonic architectures with both strong and uniform electric field hot spots. Herein, nanoscratch-induced orientational metal deposition was proposed for achieving the customizable preparation of Au plasmonic architectures on silicon (Si) for high-performance SERS detections. We found that the deposition can be significantly affected by mechanical crystal defects on Si surfaces. Based on Raman analysis and conductive atomic force microscope detections, the defects were demonstrated to change the conductivity on scratched areas. Compared with untreated scratches, conductive sites on amorphous Si-free scratches were significantly increased and distributed uniformly. Further analysis indicated that the increase in the conductivity can accelerate the redox reaction on the scratches, which facilitated the formation of compact Au structures, as confirmed by in situ scanning electron microscope characterizations. The as-prepared SERS substrates exhibited excellent detection sensitivity and reproducibility, and the anti-interference ability was demonstrated by detecting malachite green residues from different water environments. We also found that Au concentric rings with uniformly rough surfaces obtained by the proposed site-controlled deposition can focus polarization-independent electric field enhancement induced by surface defects on the whole structure surface. These findings can shed light on flexible preparation of high-quality SERS substrates.