Wafer-Scale Nanopillars Derived from Block Copolymer Lithography for Surface-Enhanced Raman Spectroscopy

Abstract

We report a novel nanofabrication process via block copolymer lithography using solvent vapor annealing. The nanolithography process is facile and scalable, enabling fabrication of highly ordered periodic patterns over entire wafers as substrates for surface-enhanced Raman spectroscopy (SERS). Direct silicon etching with high aspect ratio templated by the block copolymer mask is realized without any intermediate layer or external precursors. Uniquely, an atomic layer deposition (ALD)-assisted method is introduced to allow reversing of the morphology relative to the initial pattern. As a result, highly ordered silicon nanopillar arrays are fabricated with controlled aspect ratios. After metallization, the resulting nanopillar arrays are suitable for SERS applications. These structures readily exhibit an average SERS enhancement factor of above 10(8), SERS uniformities of 8.5% relative standard deviation across 4 cm, and 6.5% relative standard deviation over 5 × 5 mm(2) surface area, as well as a very low SERS background. The as-prepared SERS substrate, with a good enhancement and large-area uniformity, is promising for practical SERS sensing applications.

Biosensors for Studies on Adhesion-Mediated Cellular Responses to Their Microenvironment

“…Cells can be seeded on SERS substrates, and once they adhered and spread, their chemical composition near the surface can be studied by irradiating the substrate and measuring the Raman spectra. Over the years, a wide diversity of metal nanostructured surfaces have been created for SERS, such as nanoparticles attached to a surface (Freeman et al, 1995;Zhai et al, 2009;Lussier et al, 2016), nanopillars (Kang et al, 2015;Li et al, 2016), nanoholes (Abdelsalam et al, 2005;Luo et al, 2019), and others (Yüksel et al, 2017;Yao et al, 2020). A detailed review on the fabrication of SERS substrates can be found in Fan et al (2011).…”

Gold Nanoparticles Sliding on Recyclable Nanohoodoos—Engineered for Surface‐Enhanced Raman Spectroscopy

“…The remaining alumina in the nanoholes then serves as a hard mask during the following silicon etching. [35] This process reverses the pattern relative to the initial mask, rendering well ordered, hexagonally packed alumina topped silicon nanocylinder arrays over the wafer. These nanocylinders are visualized using SEM from a cross-sectional view in Figure 1b, and from a vertical view in Figure S1a (see supporting information).…”

Influence of the long-range ordering of gold-coated Si nanowires on SERS

“…The flexibility has been highlighted as an important parameter because it allows the nanowires to lean against each other and trap the molecules in the hot spots at the tip-to-tip site generating a strong enhancement 11 , 12 . Besides conventional lithographic techniques, such as electron beam lithography or focused ion beam patterning 13 – 15 , several advanced techniques have been investigated in order to obtain gold-coated NWs including nanoimprint lithography 12 , self-assembly (SA) of metallic nanoparticles 16 , diblock copolymers 17 and nanospheres lithography (NSL). Among them, one of the most promising techniques for the fabrication of high aspect-ratio NWs is given by the combination of NSL and the metal-assisted chemical etching (MACE) 18 .…”