FABRICATION AND CHARACTERIZATION OF SERS SUBSTRATES VIA LASER INDUCED PHOTOCHEMICAL SURFACE ROUGHENING OF SILICON

2022-6-10
Akbıyık, Alp
In this thesis, Surface-Enhanced Raman Spectroscopy (SERS) substrates are fabricated using laser assisted chemical etching of silicon as a surface nanostructuring technique. As a novel method of control over the structuring parameters, the incident laser illumination is spatially modified via a Digital Micromirror Device (DMD) that enable fast and uniform fabrication of complex structures. Onto the photochemically nanostructured silicon surfaces, silver and gold films are deposited by thermal evaporation or nanoparticles are formed to transform the roughened Si surfaces into the SERS substrates. The thickness of Ag and Au on the structured Si is shown to significantly alter the SERS spectra. The increase of the SERS signal is also attributed to the electromagnetic field enhancement that result from the surface roughness of Si which is controlled by the illumination power, duration and the spot size of the laser beam. For the characterization of the SERS substrates, Raman spectra of the dye molecule Brilliant Cresyl Blue (BCB) can be observed down to nM orders. Fabricated substrates are also compared under 660 nm and 532 nm excitations. Nanostructured Si surface with Ag deposition is shown to create more enhancement than Au deposition under 532 nm excitation with an enhancement factor (EF) up to 10^9. EF is calculated and SERS performance is evaluated based on both SERS and dark-field scattering spectra experimentally, and using Finite-Difference Time-Domain (FDTD) simulations, numerically. Further range of applicability of the substrates are investigated by testing with the molecules Crystal Violet (CV), Rhodamine 6G and ammonium nitrate from which large enhancements are obtained.

Suggestions

Fabrication of low reflective nanopore-type black Si layer using one-step Ni-assisted chemical etching for Si solar cell application
Takaloo, AshkanVakilipour; Kolahdouz, Mohammadreza; POURSAFAR, Jafar; ES, FIRAT; Turan, Raşit; Ki-Joo, Seung (IOP Publishing, 2018-03-01)
Nanotextured Si fabricated through metal-assisted chemical etching (MACE) technique exhibits a promising potential for producing antireflective layer for photovoltaic (PV) application. In this study, a novel single-step nickel (Ni) assisted etching technique was applied to produce an antireflective, nonporous Si (black Si) in an aqueous solution containing hydrofluoric acid (HF), hydrogen peroxide (H2O2) and NiSO4 at 40 degrees C. Field emission scanning electron microscope was used to characterize differen...
Synthesis and Characterization of Aluminum Containing Silica Aerogel Catalysts for Degradation of PLA
Sivri, Seda; Dilek Hacıhabiboğlu, Çerağ; Sezgi, Naime Aslı (Walter de Gruyter GmbH, 2019-05-01)
Aluminum loaded silica aerogel based catalysts were synthesized by impregnation of aluminum into silica aerogel produced using sol-gel method in different aluminum loadings (2.5-15 wt%) to investigate their performances in degradation of polylactic acid (PLA).
Laser induced periodic surface structuring for surface enhanced raman spectroscopy
Özkarslıgil, Zeynep Tuğçe; Bek, Alpan; Department of Physics (2020)
In this study, our aim is to fabricate and characterize efficient substrates of surface enhanced Raman spectroscopy (SERS) utilizing the field enhancement due to hot spots made by recently developed method of laser induced periodic surface structuring (LIPSS). LIPSS is a cost-effective technique for rapid processing of almost any materials compared to conventional lithography methods. Coating of a thin silver film on LIPSS applied substrate surface provides to observe the localized surface plasmon effect fo...
Characterization and Electrical Conductivity of Poly(ethylene glycol)/Polyacrylonitrile/Multiwalled Carbon Nanotube Composites
Aqeel, Salem M.; Kucukyavuz, Zuhal (Wiley, 2011-01-05)
Polymer blends based on poly(ethylene glycol), polyacrylonitrile, and multiwalled carbon nanotubes (MWNTs) were prepared by the solvent cast technique from the dispersion of the MWNTs in the concentration range 0-3.45 wt %. The interaction of the MWNTs with the polymer blend was confirmed by a Fourier transform infrared (FTIR) spectroscopy study. The thermal properties of the polymer blend with the MWNTs were carried out by means of differential scanning calorimetry (DSC). It was evident from DSC that the p...
Revealing Laser Crystallization Mechanism of Silicon Thin Films via Pulsed IR Lasers
Çlnar, Kamil; Yeşil, Cihan; Bek, Alpan (American Chemical Society (ACS), 2020-01-01)
Pulsed laser absorption-mediated explosive crystallization of silicon films has extensively been studied using microscopy techniques on single laser pulse-irradiated regions in the literature. In this work, we experimentally demonstrate and theoretically explain in detail the use of slow quenching regime for laser crystallization mediated by highly overlapping pulses. Increasing the use of Si in thin film transistors and photovoltaic applications drives researchers to find cost-effective and efficient ways ...
Citation Formats
A. Akbıyık, “FABRICATION AND CHARACTERIZATION OF SERS SUBSTRATES VIA LASER INDUCED PHOTOCHEMICAL SURFACE ROUGHENING OF SILICON,” M.S. - Master of Science, Middle East Technical University, 2022.