Optical Properties Dependence on Deposition Time for CoO(OH) Thin Films Synthesized by CBD Technique
A. N. C. Agbogu
Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria
M. P. Orji
Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria
A. B. C. Ekwealor *
Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria
*Author to whom correspondence should be addressed.
Abstract
Cobalt oxyhydroxide (CoO(OH)) thin films have been successfully deposited on glass substrates through the reaction of CoCl2, triethanolamine (TEA) and NH3 in PVP matrix using chemical bath deposition method at 333K and annealed at 423K. By changing the time of deposition as a controlling parameter from 1 – 9 hrs, the effects of dip time on the optical properties of the films were studied. The UV-VIS-NIR spectroscopy of the films revealed strong transmittance in VIS-NIR which decreased with dip time, and the absorbance of < 40% in the UV-VIS that decreased into the NIR as dip time increased. The X-ray diffraction measurement showed that the films were crystalline. The band gap energy decreased with increased dip times with values ranging from 2.10 – 2.40eV. With a refractive index ranging from 1.2 – 2.4 and good transmittance in the VIS-NIR regions of electromagnetic spectrum, the films could serve as good materials in antireflection coatings, solar energy collector and solar brooder.
Keywords: Cobalt oxyhydroxide, deposition time, CBD, band gap and optical properties