A new approach to fabricating hemispherical cavity arrays on silicon (Si) substrate using laser-assisted nanoimprinting of self-assembled particles is presented. A monolayer of silica particles, with different diameters of 0.30 and 0.97 µm, was deposited on a Si substrate by self-assembly. A quartz plate was tightly placed on the sample surface to firmly sandwich the self-assembled nanoparticle monolayer. The silica particles were imprinted into Si substrates after laser irradiation (KrF excimer laser, λ = 248 nm) on the quartz/nanoparticle/Si structure with a single pulse. Ultrasonic cleaning and hydrofluoric acid (HF) solution were used to remove the silica particles in the sample surface. Hemispherical cavities were formed on the substrate surface. The influence of laser fluence and particle size on the structuring of the surface has been investigated. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed to observe the dimensions of the cavities. One-dimensional thermal calculation was employed to calculate the thermal effects in this process.

As a powerful spectroscopy technique, surface-enhanced Raman scattering (SERS) can provide non-destructive and sensitive characterization down to a single molecular level. Aiming to the main challenges of high-performance SERS-active substrates for their real-world applications involving the ultra-sensitive and reproducible signals detection and signal uniformity with large-area, herein, a facile and reliable strategy based on combination of thermal imprinting polycarbonate (PC) film with porous anodic aluminum oxide (AAO) mold and E-beam evaporation of gold is provided to fabricate a high-quality SERS-active substrate consisting of ultra-dense hot-spots with large-area uniformity. Two kinds of sub-10 nm gaps were obtained, including the nanogaps between the neighboring gold coated PC-nanopillars and those between gold on the top of the nanopillars and that on the base, which actually build up a three-dimensional (3D) hot-spot network for high-performance SERS detection. The effect of structural parameters on SERS enhancement was investigated numerically and experimentally, and by optimizing the structural parameters, a remarkable average SERS enhancement factor up to of 1.4×108 is achieved and it shows an excellent reproducibility with a relative standard deviation of 18%, which allows for enhanced practicability in the application of quantitative biochemical detection.