Sol - Gel Characteristics Of Zno Films

Zinc oxide (ZnO) is an n-type direct band-gap semiconductor material. Due to the large exciton binding energy of 60 meV, which ensures the large exciton emission at room temperature, it is regarded as one of the most promising materials for fabricating efficient ultraviolet (UV) blue light emitting device. It's has so many properties of the ZnO thin films such as piezo-electricity, transparency conducting, optical pumping, which could be extensively used and also attracted so many domestic and international experts and scholars. That reflectes the law of "the property depends on the structure, and the use depends on the property".We choose Zn(CH₃COO)₂·2 H₂O as the precursor, 2-methoxyethanol as the solvent, monoethanolamin as the stabilizer in the experiment. We dissolve a certain Zn(CH₃COO)₂·2 H₂O in 2-methoxyethanol, and add the equal Moore of monoethanolamin. Stirring the solution for two hours, we attained the transparent and homogeneous solution whose density of the Zn ion was 0.75mol/L. The reagents used in the experiment are all analytically pure.The ZnO thin films were adopted the technique of spinning on the substrate of n-Si (100). The sample were dried at the temperature of 150℃ after each spinning. Meanwhile, in order to prepare the thicker ZnO thin films, we should repeat the spinning for five times, thus, the film thickness could reach 200-250nm. The samples were annealed to acquire the high-quality and c-axis orientation ZnO thin films. We proposed the optimal parameters through changing the annealing conditions. Firstly, only if the chemical proportion of Zn and O is one to one in the oxygen atmosphere, the crystallized quality will be improved. Secondly, we should control the annealing period of time within two hours. If the period was too long, it would result in the worse orientation of the crystalline. Lastly, we discussed the influence of the annealing temperature on the quality of the crystalline. Increasing the temperature would be helpful to therecrystallization and the optimal temperature is about 500 °C.We also get some useful conclusions through investigating the photo-luminescence (PL) of the ZnO sol and the thin films. The PL spectrum of the ZnO sol indicates: with the prolonged aging time, the ultraviolet peak shifts to the short-wave length, and the line width of the ultraviolet areas become broader, while that of the visible areas narrower. The PL spectrum of the ZnO thin films indicate that after the annealing, the ultraviolet luminescent intensity is stronger, whereas, the luminescent intensity of the visible areas weaker.We use the scanning electronic microscope observing the surface and profile of the ZnO thin films. The surface of the sample is compact and even. The profile of the sample has the well-distributed ZnO nano-particles buried in the ZnO thin films, which are consistent with the XRD calculating results.