Structural, optical, and electrical properties of copper-alloyed ZnO films deposited by the pulsed spray-pyrolysis with molecular solutions

Abstract

This study shows the effect of Cu alloying ZnO (CZO) films (x = 1–7 at.%) on their structural, electrical, and optical properties. ZnO:Cu was synthesized by the pulsed spray-pyrolysis technique using molecular solutions. CZO films were studied by XRD, SEM, EDX, Raman and optical spectroscopy, and Hall effect measurements. XRD analysis proves the formation of single-phase films with a hexagonal wurtzite structure, further confirmed by Raman spectroscopy. EDX analysis showed the successful incorporation of Cu in the unit cell of ZnO at the concentrations of x = (1–7) at.%. CZO film at x = 1 at.% possessed the best microstructure characteristics, i.e., L₍₁₀₀₎ = 22.4 nm; ε₍₁₀₀₎ = 5.9·10⁻³; ρ_εL(100) = 1.4·10¹⁶ lin∙m⁻². It was found that the band gap, E_g = 3.32 eV, in the non-alloyed ZnO films is not significatively changed upon Cu alloying, residing in the range of (3.32–3.33) eV. The low resistivity (ρ = 7.14 Ω cm) and high Hall mobility (μ = 385.91 сm²/V⋅s) were observed for the CZO films at x = 1 at.%. Thus the obtained CZO films by using the pulsed spray-pyrolysis methodology could be of interest for application in solar cells as window and charge collection layers, as determined by their properties.