Plasmonic effect of gold nanoparticles on rear side of flexible black silicon wafer fabricated by aluminum-assisted chemical etching

In this work, we investigate the effects of the different sizes of gold (Au) plasmonic nanoparticles (NPs) on the rear surface of flexible black silicon (b-Si) wafer. The flexible b-Si (65 mu m thickness) is fabricated by aluminum-assisted chemical etching (AACE) process, utilizing aluminum (Al) as the catalyst. After the b-Si fabrication, nanopores are produced on the flexible wafer surface. Then, gold nanoparticles (Au NPs) are spin-coated on the rear side of the flexible b-Si, followed by surface morphological and optical characterizations. The Au NPs with sizes of 24-92 nm have been deposited on the rear surface of the b-Si wafer. Based on the optical characterization, light absorbance increases above wavelength 800 nm due to enhanced light scattering by the Au NPs at the back surface. The average reflectance (Rave) is calculated in the 300 nm-1100 nm wavelength range for flexible crystalline silicon (c-Si) reference and compared with flexible b-Si surface and flexible b-Si/Au NPs. The lowest Rave of 15.4% is achieved for Au NPs with average size of 92 nm.