Libing Duan

Effect of annealing ambient on the structural, optical and electrical properties of (Mg,Al)-codoped ZnO thin films

Nominal 1 at.% Al-doped Zn1−xMgxO (x=0–8 at.%) thin films are prepared by the sol–gel method. The codoping films retain the hexagonal wurtzite structure of ZnO, and show preferential c-axis orientation. The effect of annealing ambient (in vacuum and nitrogen) on the optical and electrical properties of (Mg,Al)-codoped ZnO films is investigated. The transmittance of the codoping films is obviously degraded to 50–60% by vacuum annealing, but is enhanced to 70–80% after nitrogen annealing. Both the carrier concentration and the Hall mobility decrease, and the resistivity increases with the widening of the band gap in films treated in vacuum. However, the carrier concentration of films annealed in nitrogen displays fluctuations with increasing x, and the carrier concentrations of films with x=2 and 4% are higher than those of other films. The initial band gap increase of nitrogen-annealed films might be attributed both to Mg doping and to the Burstein–Moss effect due to the NO–(N2)O complex donors. In view of the transmittance and conductivity, nitrogen annealing might be a more appropriate post-annealing method than vacuum annealing for (Mg,Al)-codoped ZnO films to fulfil the requirements of transparent conducting oxide.

Controlled synthesis of SnO2 nanostructures with different morphologies and the influence on photocatalysis properties

SnO2 nanoparticles, nanoflowers, and nanorods of highly crystalline were synthesized via a simple hydrothermal method. The size and morphology of the SnO2 nanostructures could be controlled by varying the NaOH concentration of the precursor solutions. The SnO2 structures appeared to be sphere-like nanoparticles with diameters in the range of 5–10 nm in lower NaOH concentrations. In higher NaOH concentrations, the nanostructures showed orientation growth behavior and were flower-like or rod-like in morphology. The sphere-like shape demonstrated that Ostwald ripening took effect only at lower NaOH concentration while the preferential growth behavior at higher NaOH concentration testified “oriented attachment” was more suitable under this condition. Photocatalysis experiments were carried out to study the influence of the morphology, size, and surface on photocatalytic activities of SnO2. The nanoparticles synthesized with the MNaOH:MSnCl4 = 4:1 showed the highest photolytic activities owing to their tiny si...

Effect of NaZn/Nai ratio on structural, optical, and electrical properties of Na-doped ZnO thin films

In this paper, Na-doped ZnO (NZO) thin films were prepared via a dip-coating sol-gel method with Na doping content in a range of 0 at. %–3 at. %. X-ray photoelectron spectroscopy analysis showed that the NaZn/Nai ratio ( r) increased with Na doping contents from 1 at. %–3 at. %. The effect of the NaZn/Nai ratio on the structural, optical, and electrical properties of NZO thin films was investigated. As the NaZn/Nai ratio increased, the lattice constant exhibited a continuous increase and resulted in the presence of increasing compressive stress in the NZO films. When the NaZn/Nai ratio was less than 1 ( r 1, it decreased. The Hall mobility was mainly limited by ionized impurity scattering and displayed a decrease trend with the increasing NaZn/Nai ratio. Due to the Burstein-Moss effect, the optical energy band gaps ( E g) of NZO films got slightly enlarged as compared with that of the undoped ZnO film. Considering the ...

Controllable ZnO architectures synthesised on zinc substrates by hydrothermal preparation for enhanced photocatalytic activity

Abstract Controllable ZnO architectures have been achieved on zinc substrates via a versatile one-pot hydrothermal method without assistance of any surfactants or organic solvent. The morphologies of ZnO architectures have been successfully manipulated by adjusting the concentration of NaOH and temperature of the reaction system. Among the as prepared ZnO architectures, the sheet flower-like ones exhibited highest photocatalytic activity in the degradation of methyl orange (MO) under ultraviolet (UV) illumination for their nanosheets assembled structural feature.