Characterization of porous silicon thin films passivated by a nano-silver layer

This study was performed to evaluate the effect of passivation of a nano thin film of silver (Ag) on the characterization of porous silicon (PS) surface. Silver nano layers of 10 and 20 nm were deposited on a PS surface using RF-sputtering technique. The PS was prepared by electrochemical etching method (ECE) of n-type (111) Si in an electrolyte solution containing hydrofluoric acid (HF) and ethanol (C2H6O) at a volume ratio of 1:4 with direct current of 10 mA for 60 min. Structural and optical characterizations of the PS samples before and after passivation carried out using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-rays Analysis (EDX), X-ray Diffraction (XRD), reflectivity analysis using UV–vis spectrophotometer and photoluminescence (PL). These measurements show that Ag atoms regularity on the PS surface, whereas the Ag peaks confirm that increased deposition of Ag atoms on the PS surface also increases the thickness of the Ag film. The coated PS with a thin film of Ag (20 nm Ag/PS) shows enhancement in the PL and reflectivity spectra. The highest PL of 20 nm Ag/PS denotes the high electrical conductivity of Ag (63.01×106S/m) and the maximum reflectivity is attributed to the presence of surface plasmons resonance (SPR). As a result, Ag metal exhibits a negative dielectric constant at optical frequencies which leads to high reflectivity.