Enhanced light absorption in porous silicon with nanocrystalline TiO2 deposited by metal-organic chemical vapor deposition (MOCVD)
MetadataShow full item record
In this paper, nanocrystalline TiO2 thin films were successfully deposited on porous silicon (PSi) by metal organic chemical vapor deposition (MOCVD) technique for different periods of times: 5, 10 and 15 min. The objective was to improve the optical absorption properties of the porous layers dedicated for photovoltaic application. The structural, morphological and optical properties of the elaborated TiO2/PSi samples were analyzed by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), photoluminescence (PL) and UV-Visible absorption spectroscopy methods. The effect of deposition time on the microstructural properties which influence the optical characteristics of the obtained samples was also examined. The XRD analysis confirms the nanocrystalline structure of the deposited TiO2 composed only by anatase. The SEM characterization evidenced an increase in the TiO2 film thickness showing more uniform surfaces as the deposition time rises. Correspondingly, the surface roughness increases with the particle size and film thickness as indicated by AFM studies. The UV-Vis measurements showed a considerable enhancement in optical absorption of porous silicon after the deposition of nanocrystalline TiO2 films. Indeed, the TiO2 coatings deposited on PSi for 15 min with thickness of 200 nm have the best structure quality and exhibit, consequently, the highest absorption. From these interesting results, we demonstrate the viability of the use of the MOCVD as reproducible process for the elaboration of highly efficient antireflective layers.