Influence of Co loading on structural and morphological properties of Co-doped ZnO thin films grown by pulsed electron beam ablation

Highlights: • Deposition of Co-doped ZnO films on high temperature pre-annealed substrates. • Effects of target Co loadings on properties of the films have been assessed. • The films growth can be substantiated by two models. • Metallic Co content increases in the films as Co loading in the target increases. We report on the effect of cobalt loading in the target material on the properties of thin film nanocomposites of Co-doped zinc oxide (CZO) Zn_1-xCo_xO. The films have been deposited by pulsed electron beam ablation (PEBA) at 450°C on pre-annealed (1100°C) c-sapphire and Si (100) substrates. The experimental results, based on scanning electron and atomic force microscopies (SEM, AFM), indicate that Co doping significantly affects the morphology of the films. X-ray diffraction (XRD) measurements reveal that the films on both substrates exhibit a prominent ZnO hexagonal wurtzite structure for x = 0.05, whereas higher Co loading (x = 0.1, 0.2) results in a strong deformation of ZnO wurtzite lattice and in a higher content of hexagonal close-packed (hcp) metallic Co in CZO films. X-ray photoelectron spectroscopy (XPS) data confirm the presence of non-oxidized metallic Co (Co°) in the deposited films. Both XRD and XPS results indicate an increase in Co° content in the films as Co loading in the target is increased.