Morphology, structure and emission of Al-doped ZnO nanocrystal films

The morphology, structure and emission of Al-doped ZnO nanocrystals (NCs) with the different Al contents (1–4 at.%) were studied by means of the scanning electronic microscopy, energy dispersive X ray spectroscopy, X-ray diffraction and photoluminescence (PL) methods. Ultrasonic spray pyrolysis was applied to obtain the ZnO:Al films. To stimulate the crystallization, the ZnO:Al films were annealed at 400 °C for 4 h in a constant nitrogen flow (8 L/min). It is shown that the Al incorporation in the ZnO films with the concentrations of 2–4 at.% stimulates: the reduction of ZnO:Al grain sizes, decreasing the film crystallinity owing to disordering the ZnO:Al crystal lattice, the change of the surface morphology and increasing the surface roughness. Meanwhile, Al-doping the ZnO films at the concentrations ≤ 2 at.% enlarge significantly the PL intensity of the near band edge emission. Last fact testifies to quality improving the ZnO:Al films. Simultaneously, the PL intensities of green and orange PL bands, connected with the native defects: V_Zn and O_i, fall down. The ZnO NC films with Al-doping ≤ 2 at.% still keep the planar surface morphology that is important for their applications in electronic device structures.