Film Thickness Effect on Properties of Co-ZnO Thin Films Prepared by Sol-Gel Method

Authors M. Medjaldi1, N. Dadda2, A.R. Khantoul3, I. Ameur4, A. Kassaa3, A. Boumaiza4, B. Boudine4, M. Sebais4

1Laboratory of SATIT, University Abbes Laghrour Khenchela, Algeria

2Laboratoire de Synthèse et Biocatalyse Organique (LSBO), Département de Chimie, Université Badji Mokhtar Annaba, B.P. 12, 23000 Annaba, Algeria

3Research Center in Industrial Technologies CRTI, P. O. Box 64, Cheraga 16014 Algiers, Algeria

4Crystallography Laboratory, Physics Department, Faculty of Exact Sciences, Mentouri Brothers- Constantine 1 University, Route Ain El Bey, 25000 Constantine, Algeria

Issue Volume 14, Year 2022, Number 6
Dates Received 01 November 2022; revised manuscript received 22 December 2022; published online 27 December 2022
Citation M. Medjaldi, N. Dadda, et al., J. Nano- Electron. Phys. 14 No 6, 06023 (2022)
PACS Number(s) 81.20.Fw,, 68.55.jd, 68.55.J_, 78.68._m
Keywords Co-doped ZnO thin films, Dip-coating, Thickness (13) , Photoluminescence (17) , XRD (80) , Electrical conductivity (10) .

1 wt. % Co-doped ZnO (CZO) thin films of varying thicknesses (3, 5 and 7 layers, which correspond to 403, 545 and 725 nm as thickness) are deposited using the sol-gel method onto glass substrates by dip coating technique. Zinc acetate dehydrate, cobalt acetate, 2-methoxyethanol and ethanolamine are used as primary materials, solvent and stabilizer, respectively. The thermally annealed films are characterized to study the structural, surface morphology, electrical and optical properties. X-ray diffraction (XRD) shows that these films have a polycrystalline hexagonal structure (wurtzite structure with space group P63mc), possessing compressive stress and presenting a preferred orientation along the (002) plane. We note that the particle size increases when the thickness increases. The surface morphology of the prepared CZO thin films is investigated by atomic force microscopy (AFM). It reveals the emergence of a uniform columnar structure and shows that the particle size and the root mean square (RMS) of CZO increase with increasing thickness. UV-visible spectroscopy shows (in the visible region) a transmittance between 75 and 86 % for all the films, strong absorption (in the UV region) and a decrease in the optical band gap. Moreover, the near band edge (NBE) and visible emissions detected by photoluminescence are affected by the thickness. The electrical conductivity of the sample with 725 nm is found to be 4.43 (cm) – 1.

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