Скачать или смотреть VII.22. Effect of the deposition times on Co3O4 thin films prepared by spray pyrolysis

NOM : DARENFAD
Prénom : Warda
Affiliation : Thin Films and Interfaces Laboratory (LCMI), University Frères Mentouri of Constantine 1, 25000 Constantine, Algeria
Courriel : [email protected]
Résumé : Cobalt oxide (Co3O4) thin films were deposited onto amorphous glass substrates using a spray pyrolysis technique from cobalt nitrate thexahydrate dissolved in distilled water. The objective of this work is to study the effect of deposition time (4, 5, 6 and 8 min) on the structural, optical and electrical properties of these films, in order to optimize this parameter. We then performed analyzes on the samples produced by different characterization techniques such as: X-ray diffraction, scanning electron microscopy (SEM), UV-visible spectroscopy and the Hall effect. XRD study showed that all the films were polycrystalline consisting of Co3O4 spinel cubic phase with a preferential orientation in the direction (311). The variation of the crystallite size and deformations vary inversely with increasing deposition time. The FTIR and Raman results confirm the presence of Co+2 cations located at tetrahedral sites and Co+3 at octahedral sites, which confirms the spinel-like cubic structure. The morphological study by SEM and the contact angle showed that the morphology of the film surface is rough, contains bubbles and pores for low time which correspond to the hydrophilic structure, the increase in the deposition time leads to an increase many bubbles and the structure becomes hydrophobic. Optical measurements have shown that the deposited layers of Co3O4 have a high absorbance in the visible region with the presence of two optical gaps (Eg1 and Eg2). Hall effect measurements indicate that thin films of Co3O4 are p-type semiconductors. The maximum resistivity measured is 6.879 (Ω. cm) for a deposition time equal to 8 min.