Controllable Fabrication Of ZnO Micro/nano Architectures And Properties Characterization

Zinc Oxide is a kind of semiconductor with a direct band gap of 3.37 eV at room temperature and exciton binding energy of 60 meV. On behalf of the large exciton binding energy, the exciton can keep stable under room temperature, which makes it potential for blue-ultraviolet and white light-emitting devices, as a substitution of GaN.In this thesis, the growth of micro/nano ZnO material was controlled by hydrothermal method and their optical, electrical and magnetic properties were studied. After the ZnO micro-/nano-rods, rods based thin film, porous spheres and porous film were successfully fabricated by controllable growth process, we figured out the growth mechanism of these structures. Both the substrate coated with ZnO seed layer and sodium citrate in the precursor solution played a key role in leading the products. The citrate anions not only modify the morphology but also decide the phase of the grown zinc compounds. The ZnO thin layer coated on glass substrate is used to control the nucleation event and finally modifies the morphology of the grown ZnO. In conclusion, we can selectively grow the four kinds of structures mentioned above through the control of ZnO seed layer and precursor solution.We continued to study the conduction of nano rods based thin film, and it was found to have predominantly electrical properties. Its carrier mobility is as high as 54.8 cm2·V-1·s-1 and concentration-2.73x1018 cm-3. Simple growth process, low cost and superior conductivity make this film of great potential for practical application. In order to understand the mechanism of conduction, photoluminescence, electron paramagnetic resonance, Fourier transform infrared spectra and X-ray photoelectron spectroscopy were used to analyze its crystal structure and internal properties. A high concentration of interstitial hydrogen existed on the surface of nano rods, which may be the source of most carriers in the film. We also studied the optical and magnetic properties of the ZnO porous spheres. They can be obtained through thermal decomposition of Zn5(OH)8Ac2·2H2O or LBZA, which was reported for the first time. The BET surface area of this kind of ZnO reached 42 m2/g. It's interesting that porous ZnO shows significant room temperature ferromagnetic even without any transition metal doping. In order to found out the origin of the room temperature ferromagnetic, we systematically analyze its micro structure and related physical properties with the help of X-ray photoelectron spectroscopy, electron paramagnetic resonance, photoluminescence and SQUID. It turned out to be the shallow donors caused by hydrogen perhaps play an important role in triggering magnetic order in ZnO samples. Hydrogen should be located on the surface of the material combined with the atom of zinc.