| Summary: | 碩士 === 國立中央大學 === 材料科學與工程研究所 === 99 === An attempt was made in his work to fabricate nano structure zinc oxides on zinc foil (10 mm x 10 mm x 0.62 mm) from the alkaline solution containing zinc ions by electrochemical method. In this system, zinc was the working electrode, stainless steel (ss) 304 was the counter electrode and Ag/AgCl was the reference electrode. After polishing to obtain mirror surface, the zinc foil was potentiodynamically polarized in 2M NaOH solution containing 0.00 M, 0.15M, 0.20M, 0.25M Zn(NO3)2 and 0.20M NaNO3, from the potentials at which the open circuit potentials (OCPs) minus 0.250V to 2.00V(vs. SHE) by the aid of Potentiostat 273A, with the scan rate at 1mV/s. The open circuit potential is at about -1.20V (vs. SHE), and it increases with the concentration of zinc ions. Electrolysis at -0.87V, the current will decrease to the lowest value so that it is a critical potential to have an abrupt change in current density. This potential is the boundary between active region and passive region. According to the polarization diagram, we conducted potentiostatic electrolysis at -0.5V, -0.7V, -0.9V, and -1.1V, respectively. And examined the morphology of the deposits with field-emission scanning electron microscope (FESEM), we found that the deposits fabricated at -0.5V and -0.7V are in nano single crystalline wires of ZnO (250 nm in length and 25 nm in diameter), and there is no clear difference when Zn(NO3)2 at 0.15M~0.25M. However, those fabricate at -0.9V and -1.1V are in polycrystalline nano sheets (200 nm in diameter and 25 nm in thickness) , and 0.25M Zn(NO3)2 has better morphology. Analysis by Energy-dispersive X-ray spectroscopy (EDX), we found that these two different structures have almost the same composition with the ratio between zinc and oxygen about 1:1. Analysis by X-ray photoelectron spectroscopy (XPS), we confirmed the composition of ZnO in which the peak Zn(2p3/2) at 1021.9 eV belonging to zinc oxide. X-ray diffraction (XRD) measurement demonstrated the crystal is a wurtzite of hexagonal with a texture of (002). Analysis by Photoluminescence (PL), we found that these two different structures have a peak at 380nm, and this peak belong to ZnO intrinsic peak. The other peak is due to impurities and defects.
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