| ZnO is a direct wide band gap compound semiconductor materials, which has the hexagonal wurtzite type crystal structure. Its band gap is3.37eV at room temperature and exciton binding energy is60meV. ZnO thin films have high resistance rate and good C-axis preferred orientation, which makes them good piezoelectric constant and electromechanical coupling coefficient. The un-doped ZnO films are unstable and not suitable to be used for the preparation of materials. ZnO not only has excellent optical and electrical properties, chemical stability, but also has high thermal stability, and is very easy to carry out the various elements of the doping. Doping can improve its performance in various fields.This thesis describes the latest research and development of ZnO. We introduce the doped direction and the structure and properties of the doped ZnO thin films. Study the impact of different variables on the optical and electrical properties of rare earth elements doped ZnO thin films, providing a wealth of reliable experimental data for this new research direction. At the same time, we also raise some of the content of rare earth doped films and some of this research direction yet to be developed.In this study, we use the sol-gel method and dip-coating process to prepare the rare earth elements (Y3+, Nd3+) doped ZnO thin films. Study the influence of doping concentration, coating layers, and the heat treatment temperature in the crystal structure of the film surface morphology and the optical and electrical properties. The main research is that preparing the thin films doped by Y3+or Nd3+through sol-gel method. We select the doping concentration is1%,2%,3%, the coating layers is20layers,25layers,30layers, and the heat treatment temperature is470℃,500℃and530℃. We use X-ray diffraction (XRD), scanning electron microscopy (SEM), UV spectrophotometer, Raman spectrometer and other equipment to analyze the crystal structure, surface morphology, grain size, square resistance of the film samples.Through the analysis of the prepared samples, we have come to the results that we prepare the YZO (ZnO:Y) thin films successfully, and Y3+successfully doped into the ZnO lattice. Y3+incorporation makes ZnO lost the original (002) orientation, thus, the (101) and (001) diffraction peak has been enhanced. YZO films have dense and uniform surface. The internal structure is like reticular. The average transmittance of the films is more than70%, the light transmittance shows a certain regularity with the increasing of Y3+concentration. With the increase of the coating layers, the transmittance of the films decreased. The heat treatment temperature can enhance the preferred orientation of the films, making the crystal larger and it also make the transmittance of the films increase. For NZO(ZnO:Nd) thin films, the preferred orientation of the NZO (ZnO:Nd) films completely disappeared, but there have been three main characteristic peaks of wurtzite-type ZnO. And with the of Nd3+doping concentration increases, the film grain have refinement. By the sol-gel method, we prepared the flat surface films, which have the needle-like morphology. With the temperature increasing, the absorption edge of the film blue shift. After optimization of various parameters, we get the best Y3+doping optimum conditions: Y3+doping concentration is1%, the coating layers are20layers, heat treatment temperature is530℃, the heat treatment time is2h, the drying temperature is120℃. The best optimum conditions of Nd3+ doped films:Nd3+ doping concentration is3%, the coating layers are20layers, the heat treatment temperature is500℃, heat treatment time is2h, drying temperature is120℃. The cooling method is cool the films with the furnace temperature to room temperature. |
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