PREPARATION AND PHYSICAL CHARACTERIZATION OF NANO POROUS SILICON TO TAKE ADVANTAGE OF IT IN SOME ENVIRONMENTAL APPLICATIONS

Abstract

Porous silicon (PSi) has emerged as a potential sensing applications because of its high surface area to volume ratio, convenient surface chemistry, and very low toxicity. Porous silicon layers have been prepared from non-polished p- type silicon wafers of (100) orientation using electrochemical etching with different electrolyte concentrations and etcning time. Scanning electron microscopy (SEM), photolumincence (PL) spectroscopy, spectrophotometer measurement and Fourier Transform Infra Red (FTIR) have been used to characterize the morphological and optical properties of porous silicon. The influence of fabrication parameters (hydrofluoric acid (HF) solution, the anodizing current density and anodizing time) on the morphological and optical properties of porous silicon has been investigated. SEM micrographs showed that by changing HF: ethanol concentration ratios, in the electrochemical process, peculiar surface morphology was obtained. The surface morphology in the central region of the sample consists of solid cells delimited by trenches and the trenches bottom was covered by polyhedral pores. The PL spectrum peak at the anodizing time ranged from 590 to 610nm. PSi samples showed lower reflectance measurements and the optical energy band gap increases with increasing etching time.The effect of immersing PSi in distilled water on PL intensity and reflectance were studied,the obtained FTIR spectra were in the range of 600 to 4000 . It could be clearly seen that porosity of PSi layers increases with increasing etching time and dilution of the electrolyte concentration which reflect on both increasing of PL intensity and decreasing reflectance with increasing porosity that gives the ability for using PSi in solarcells and bio sensing applications.