Effect of reaction time on structural properties of ZnO:Al films

Undoped and Al doped ZnO films are obtained by chemical bath deposition onto glass substrates. Investigations of the effect of reaction time on structural and sub-structural features were carried out using high resolution scanning electron microscopy (SEM) and X-ray diffraction analysis. The effects of deposition time on elemental composition are found. Deposited ZnO and ZnO:Al films have a hexagonal structure with growth texture of [002]. Lattice constants of undoped material weakly depend on the time of synthesis and vary in the range of a = 0.32486–0.32548 nm, c = 0.52064–0.52149 nm. Simultaneously, lattice constants of Al doped ZnO films vary in the wide range: a = 0.32490–0.31997 nm, c = 0.52293–0.52116 nm. The coherent scattering domain size (CSD) of undoped ZnO are in the range of (L₍₁₀₀₎ = (24.5 - 27.3) nm, L₍₀₀₂₎ = (26.4–28.8) nm, L₍₁₀₁₎ = (25.0 - 27.1) nm). In the ZnO:Al films the CSD size increased with increasing the duration of their synthesis from 45 to 90 min (L₍₁₀₀₎ = (19.5 - 52.3) nm, L₍₀₀₂₎ = (23.2 - 55.0) nm, L₍₁₀₁₎ = (17.6 - 48.3) nm). Further increase of reaction time up to 120 min led to a significant reduction of the CSD size in all crystallographic directions (L₍₁₀₀₎ = 38.0 nm, L₍₀₀₂₎ = 39.0 nm, L₍₁₀₁₎ = 39.4 nm) which was due to the peculiarities of ZnO:Al growth.