Elaboration and characterization of oxide thin films with suitable dielectric constant by soft chemistry for microelectronic applications

BEN MESSAOUD, Ouarda (2025) Elaboration and characterization of oxide thin films with suitable dielectric constant by soft chemistry for microelectronic applications. Doctoral thesis, Université Mohamed Khider (Biskra - Algérie).

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Abstract

This study investigates the synthesis and characterization of copper oxide (CuO) thin films and ZnO: CuO composite films deposited using the pneumatic spray technique (PST) on glass substrates under various conditions. The structural, morphological, surface texture, optical, and electrical properties of the films were analyzed using XRD, SEM, EDS, profilometry, UV-Vis-NIR spectroscopy, and four-point probe measurements. The results indicate that spray pyrolysis is an effective method for fabricating semiconductor oxide thin films with tunable properties. CuO films deposited with varying precursor concentrations, deposition times, and different copper salts exhibited monoclinic structures with a (-111) and (111) preferred orientations. SEM images show uniform, adherent, homogenous and well-covered surfaces free of pores and cracks. Surface roughness has a direct correlation with thickness. The average transmittance and reflectance of the films is in the range of 60-80% and less than 40%, respectively. The optical band gap is of the range (2.19–2.72 eV). The optimal deposition time is 3 min. Electrical conductivity varied depending on deposition parameters, with copper acetate yielding the highest conductivity. The optical constants such as extinction coefficient, refractive index and dielectric constant were calculated. The film deposited at 0.025 mol/L for 3min by using copper chloride precursor, exhibits the highest real part of the dielectric constant (ԑr ~ 17 at 800 nm) that can be used as dielectric layers for optoelectronic devices working in Vis-NIR region of radiation. The film ZnO: CuO composite films demonstrated a polycrystalline structure with both ZnO (wurtzite) and CuO (monoclinic) phases. Increasing Cu content affects crystallite size, morphology, and optical properties. The optical band gap ranged from 3.18 to 1.5 eV, and conductivity decreased with higher Cu content. These findings highlight the potential of CuO and ZnO: CuO films for microelectronic and optoelectronic applications, with future work suggested on ternary oxide composites.

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