Improved SERS Intensity from Silver‐Coated Black Silicon by Tuning Surface Plasmons

Abstract

Surface plasmon waves have been widely utilized to enhance the light-matter interaction near the surface of the structures for a broad range of sensing methods, including surface plasmon spectroscopy, [1][2][3][4] plasmon-controlled fl uorescence [ 5,6 ] and surface-enhanced Raman scattering (SERS). [7][8][9] In particular, SERS has been demonstrated as one of the most important and promising approaches for various applications [10][11][12][13][14] (e.g., high-sensitivity bio-sensing down to a single-molecule level [ 7,15 ] ), because of its effective identifi cation of chemical bonds. Numerous nanostructures have been investigated to effectively improve the electromagnetic enhancement, a predominant mechanism contributing to the total enhancement in light-matter interaction. [ 16,17 ] Among these nanostructures, periodic metal nanostructures fabricated by e-beam lithography (EBL) or focused ion beam (FIB) patterning, [18][19][20] have been widely utilized to investigate the light-matter interaction mechanism, especially coupling effects such as nearfi eld dipole and long-range interactions, because of the merit of adjustable nanostructure dimensions in these methods. In addition, a few disordered nanostructures (e.g., gold nanoparticle dimers and trimers, [ 7,21,22 ] silver (Ag) nanowires, [23][24][25][26] Ag nanoparticles decorated nanotrees [ 27 ] or nanorods [ 28 ] ) fabricated by various methods (e.g., chemical reduction process, [ 29,30 ] Langmuir-Blodgett technique, [ 23,24 ] self-assembled synthesis [31][32][33] ) have attracted considerable attention. In contrast to the periodic nanostructures, disordered aggregates of metal nanostructures also can result in extremely high fi eld enhancement, which is typically observed on the so-called "hot spot" sites. [ 34 ] Indeed, these periodic and disordered nanostructures have been extensively investigated, addressing their potential for various applications. [ 35,36 ] However, the aforementioned fabrication methods have their drawbacks. For example, the nanofabrication methods such as EBL [ 18,19 ] and FIB [ 20 ] require expensive equipments and are typically time-consuming for large-scale applications. The chemical methods (e.g., chemical reduction process, [ 29,30 ] Langmuir-Blodgett technique [ 23,24 ] ) usually are inapplicable due to the challenges of repeatability control in these fabrication processes for applications, where high fi eld enhancement is required. Therefore, novel fabrication methods for simple, cost-effective, large-area nanostructure devices with high enhancement factors (e.g., >10 9 ) [ 37 ] are thus of great importance for various practical applications (e.g., SERS, [ 38 ] plasmon-enhanced fl uorescence [ 39 ] ).Black silicon (BS) is a nano-roughened silicon (Si) surface, which can be produced by a wide variety of dry and wet etching techniques. Initially discovered as an unwanted side-effect of dry etching, it has gathered a lot of attention lately due to the low-cost and simple process to achieve nanostructures on a large scale. The na...

Enhancing light trapping of macroporous silicon by alkaline etching: application for the fabrication of black Si nanospike arrays

“…During the second stage of AE (after 1 min), the surface reflectance increased, due to the lowering of the aspect ratio of the nanostructures, as shown in Figure 2 We now pay special attention to the Si NSpike arrays that presented the best light trapping because they are very promising for energy conversion, SERS or biomimetic antibacterial devices. [10][11][12] More samples were prepared using the protocol described above (with an AE time of 1 min) and were further characterized, as shown in Figure 4. In the low magnification view (Figure 4a), it can be seen A c c e p t e d m a n u s c r i p t that the NSpikes covered the whole surface of the Si wafer with a grass-like fashion (see also Figure S9), based on analyses of SEM top views, the surface density was estimated to be 7 x10 4 mm -2 .…”

“…Due to the potential scalability and the simplicity of the method, it is highly promising because such arrays could have straightforward applications for various Si-based devices, in particular for improving the performances of SCs, 5 as well as in artificial photosynthesis for producing highly efficient Si-based PECs photoelectrodes. 1 Last but not least, such spikes would be appealing for ultrasensitive biodetection devices based on surface-enhanced Raman scattering (SERS) 11 or for designing antibacterial materials. 12 A c c e p t e d m a n u s c r i p t A c c e p t e d m a n u s c r i p t…”

“…1,4,6,7 In this context, top down micro-and nanostructuration of mono-or polycrystalline Si surfaces is highly appealing for boosting photon absorption and enlarging surface areas while conserving the properties of bulk Si. The fabrication of structured and highly absorbing Si, referred as Black Si (BSi), is, therefore, a very active research topic in materials with applications for renewable energy and photonics [1][2][3][4][8][9][10] and also, as recently demonstrated, for designing efficient surface-enhanced Raman scattering (SERS) 11 surfaces or biomimetic antibacterial materials 12 . Several techniques can be used to enhance light absorption.…”

Surface-Enhanced Raman Scattering of Silicon Nanocrystals in a Silica Film

“…Very high enhancement factors have been demonstrated and the measurements of single molecules adsorbed on metal films have been performed using this method1920212223. Fabrication of SERS substrates with nanoscale features is a principal issue in the area2425262728, and metal-coated Si nanostructures have been used for this purpose29303132. Another approach to SERS is to deposit a metal island film on a top of the sample (overlayer method)333435363738.…”

Silver hierarchical structures grown on microstructured silicon in chip for microfluidic integrated catalyst and SERS detector

“…Black silicon (BS) is widely researched in the areas of photodetectors, solar cells, and sensors since it has many remarkable properties, such as a large absorption range and a highly effective surface area [1][2][3][4][5] . When its micro/ nano-roughened surface is coated with metal nanoparticles, BS could be utilized for various other applications, such as surface-enhanced Raman scattering (SERS) sensors [6][7][8] . For instance, silver-covered BS with nanopillar forests could work as a SERS active biosensor [9] .…”