Structural, morphological and optical properties of atomic layer deposited transition metal (Co, Ni or Fe)- doped ZnO layers

In this work, the feasibility of atomic layer deposition (ALD) to prepare transition metal (Ni-, Co- or Fe-) doped ZnO thin films have been studied. The effects of dopant on the structure, morphology and optical properties of films have been investigated by a number of various techniques: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ellipsometry, UV–Visible spectroscopy, Fourier transformed infrared spectroscopy (FTIR). The effect of substrate (glass, Si with different conductivity type and orientation) on the morphology of layers has also been studied. All layers have a hexagonal wurtzite structure but the preferential orientation of crystallites depends strongly on the dopant. In the case of Ni-doping, the results unambiguously reveal the incorporation of Ni in ZnO lattice. NiO clusters are also possibly formed in Ni:ZnO layers which can explain the observed significant decrease of their transparency. The investigations imply that under the doping scheme and technological conditions used in this study Co and Fe are incorporated only in small amounts in ZnO. Co-doping improves the transparency of ZnO films. The possibility to deposit thin homogeneous films of transition metal (Ni-, Co- or Fe-) doped ZnO by ALD method opens-up new frontiers for implementation of these materials in advanced electronic, magnetic or optical applications.