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Hydrothermal synthesis of ZnO powder and its morphology changes

Author: ZhaoWei
Tutor: ZhouJianPing
School: Shaanxi Normal University
Course: Condensed Matter Physics
Keywords: Hydrothermal method ZnO powder Morphology Mechanism Diluted magnetic semiconductors
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 144
Quote: 1
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Abstract

ZnO as a direct band gap semiconductor material with piezoelectric, photovoltaic and doped with transition elements exhibit magnetic. Since the band gap of 3.37eV and exciton binding 60eV, as good a substitute for GaN, is expected to become the next generation of light-emitting materials. Light-emitting diodes and laser has great application prospects become in recent years the research focus. Hydrothermal method in many of ZnO as a process simple, inexpensive method for the preparation of ZnO powder. Hydrothermal Preparation of ZnO experimental factors influence the results, the regularity of the experiment. Research reports generated by the hydrothermal method experiments with flower-like structure of ZnO generation mechanism is not a lot. ZnO dilute magnetic study of Co-doped ZnO system has little to report. This article prepared by hydrothermal method ZnO, for more than about three main research content and results are as follows: first: experiments under different reaction conditions, the study of different reaction conditions on the the ZnO morphology of the resulting impact, respectively. changing the temperature, time, the reaction pH, and adding different additives in the experiment. The conclusion of the reaction: The more crystallinity complete With time increasing ZnO particles generated growing. And when the temperature was gradually increased, ZnO by small crystals particulate to rod-like ZnO crystal and then to have a process of change of the structure of the three-dimensional structure of ZnO Nanoflower with. The pH values ??for ZnO morphology is significantly reduced as the pH value increases the particle size. The flower-shaped structure at a pH of 9 and 9.5. The different additives morphology also have a great impact. The second: a preliminary study of the growth process and formation mechanism of the flower-like structure of ZnO and its luminescent properties are discussed. The process is generated using the The ZnO rod surface defect at the node, and the formation of a two-dimensional cross-shaped structure, and then again to the intersection point for the node, generating the three-dimensional structure of the ZnO. ZnO of PL spectroscopy results show that the intrinsic emission peak near 400 nm as the pH increases, the relative intensity gradually becomes weak, caused by the deep level defects 600nm emission peak near the relative intensity gradually becomes larger, and the emergence of a wide range of blue shift. Studies have shown that the PL spectra before and after annealing of ZnO, the annealing can effectively reduce the concentration of defects in ZnO. Third: excessive group elements Co doping of ZnO dilute magnetic semiconductor. Ordinary hydrothermal method, the maximum doping concentration of Co in the ZnO system is 5%, also studied the influence of different hydrothermal environment on the doping concentration of Co, the study results show that with the increase of the pH value , the doping concentration of Co in ZnO will be slightly increased. The Co doped makes anisotropic weakening of ZnO, ZnO nanorods appear shorter. Hysteresis loop test, the Co-doped ZnO ferromagnetic at room temperature.

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