Abstract
In this paper, we present a fast fabrication of Al/Si nanopillars for an ultrasensitive SERS detection of chemical molecules. The fabrication process is only composed of two steps: use of a native oxide layer as a physical etch mask followed by evaporation of an aluminum layer. A random arrangement of well-defined Al/Si nanopillars is obtained on a large-area wafer of Si. A good uniformity of SERS signal is achieved on the whole wafer. Finally, we investigated experimentally the sensitivity of these Al/Si nanopillars for SERS sensing, and analytical enhancement factors in the range of 1.5 × 10 − 2.5 × 10 were found for the detection of thiophenol molecules. Additionally, 3D FDTD simulations were used to better understand optical properties of Al/Si nanopillars as well as the Raman enhancement.
Highlights
During this last decade, Surface Enhanced Raman Scattering (SERS) is mainly employed as a powerful technique for detection of biological/chemical molecules
On all SERS spectra, we observed Raman shifts, which are characteristic of thiophenol molecules [38,39,40] as those at 1000 cm−1 corresponding to the C-C stretching mode (named: ν(CC ), see References [40,41,42]); at 1025 cm−1 corresponding to the combination of the following modes: C-C stretching and C-H in-plane bending (named: ν(CC ) and δ(CH ), respectively, see References [40,41,42]); at 1075 cm−1 corresponding to the combination of the following modes: C-C
Other groups have demonstrated good enhancement factors (EF) with similar SERS substrates such as Ag nanoparticles on Si nanowires, and Si nanopillars covered on the nanopillar top by Ag lumps (EF ∼5 × 106 ) [25]
Summary
Surface Enhanced Raman Scattering (SERS) is mainly employed as a powerful technique for detection of biological/chemical molecules. Several groups investigated a great number of novel SERS substrates, which demonstrated a large Raman enhancement, such as colloidal metallic nanoparticles [1,2,3] and metallic nanostructures on different surfaces fabricated by various lithographic techniques [4,5,6,7,8,9,10,11]. Nanoimprint Lithography (NIL) [18,19,20] and Nanosphere Lithography (NSL) [21,22,23] allows fabricating these SERS substrates with a lower cost They can be plagued by poor definition of nanostructures obtained on large surfaces, which are required for practical/industrial applications. Disordered SiNWs can be fabricated by large-surface techniques All these SERS substrates have great potential for a very sensitive detection of chemical or biological molecules, most of the applications are hampered by the non-uniformity of the SERS signals. To further deepen the comprehension of the SERS signal enhancement, 3D FDTD simulations are made
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