Characterization of Ag-porous silicon nanostructured layer formed by an electrochemical etching of p-type silicon surface for bio-application

Nanostructured layers composed of silver-porous silicon (Ag-PS) have been formed by an electrochemical etching of p-type (1 1 1) silicon substrate in a AgNO3: HF: C2H5OH solution at different etching times (10 min-30 min). Scanning electron microscopy (SEM) and energydispersive x-ray spectroscopy (EDS) results reveal that the produced layers consist of Ag dendrites and a silicon-rich porous structure. The nanostructuring nature of the layer has been confirmed by spatial micro-Raman scattering and x-ray diffraction techniques. The Ag dendrites exhibit a surface-enhanced Raman scattering (SERS) spectrum, while the porous structure shows a typical PS Raman spectrum. Upon increasing the etching time, the average size of silicon nanocrystallite in the PS network decreases, while the average size of Ag nanocrystals is slightly affected. In addition, the immobilization of prokaryote Salmonella typhimurium DNA via physical adsorption onto the Ag-PS layer has been performed to demonstrate its efficiency as a platform for detection of biological molecules using SERS.