Influence of pulse repetition rate on the growth of cobalt-doped ZnO thin films by pulsed electron beam ablation

Cobalt-doped ZnO (CZO) film nanocomposites have been deposited on Si(100) substrates by pulsed electron beam ablation from a single Co0.2Zn0.8O target. The films have been deposited at various electron beam repetition rates (1, 2, 4, and 8 Hz), under a background argon (Ar) pressure of ∼3 mtorr, an accelerating voltage of 16 kV, and a deposition temperature of 450 °C. The effect of beam frequency on the structural, chemical, and morphological properties of the films has been assessed. The findings reveal that film thickness, film roughness, and degree of crystallinity of the ZnO wurtzite structure increase with beam frequency, while globule size and density reach maximum and minimum values, respectively, as the beam frequency is increased. The pulse frequency does not appear to affect the average nanoparticulate size. X-ray photoelectron spectroscopy data support the co-existence of metallic cobalt (Co0), CoO, and Co2O3 in CZO films near the surface. Phase analysis by X-ray diffraction also confirms the presence of hexagonal close-packed metallic cobalt whose content in the films is practically unaffected by beam frequency.