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Correlation between structural and optical properties of SiO2/TiO2 multibilayers processed by sol-gel technique and applied toBragg reflectors

H.Sedrati, R.Bensaha, M.Brahimi, H.Dehdouh, H.Bensouyad, F.Abbas, B.Toubal

SiO2 and TiO2 thin layers processed by sol-gel technique have been deposited, alternatively, on glass substrates and Si (111) wafer. Dip-coated multibilayerswere characterized by different experimental techniques:XRD, SEM, FTIRandUV-VIS-NIR. The obtainedX-ray diffraction patterns analysis have shown that our films crystallize in anatase and rutile phases whatever is the number of bilayers and the corresponding grain sizes increase from 5.48 nmto 16.11 nm. The SEMmicrograph shows that our layers are homogeneous without any visual cracks. The FTIR spectra have shown that the vibration of Si-O-Ti bonds becomes intense by the increase in the number of bilayers. This increase, on the on hand, decreases the transmission coefficient from 4.58% to 0.55% and increases the width of the stop band shown in UV-VIS-NIR spectra. On the other hand, the band-gap decreases from3.73 eV to 3.59 eV. In addition, a pseudo band-gap is located between 300 nmand 400 increasing from1.76 eVto 2.29 eV.