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

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; ρεL(100) = 1.4⋅1016 lin¿m􀀀 2. It was found that the band gap, Eg = 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.