Fabrication And Photoluminescence Properties Of Porous Anodic Alumina Templates

Porous anodic alumina(PAA)films were formed on the surface of pure aluminum by anodic oxidation in acid electrolytes. The pore diameter and the inter pore distance of PAA are in nanometer scale and can be controlled by the anodizing conditions, and the pores array is of high uniformity and with high ratio of length and diameter. The characters mentioned previously make the PAA films are widely used as the templates to fabricate one dimension nano-materials.In this paper, two-step anodization was used to fabricate PAA films with the pore diameter ranges from 20 to 100nm, in the electrolyte of oxalic or sulfuric acid. Based on the analysis of pore structure according to SEM images of PAA, the effects of the anodizing voltage, the concentration of electrolyte and the structure of aluminum annealed at different temperature on the structure and the uniformity of PAA were researched systematically. In addition, the mechanics of the effects were studied according to the change of current density during the anodizing. The following results can be concluded:The pore diameter and the inter pore distance increase linearly with the increasing of the anodizing voltage. The pore diameter enlarges but inter pore distance does not along with the increasing of the concentration of oxalic acid. The uniformity of PAA was improved with increasing the annealing temperature of the aluminum. In addition, alumina nanowires (ANW) were obtained when the anodizing voltage is above 60V. The collapses of the thinner inner wall of PAA and the formation of ANW were researched based on the SEM images of the samples at different anodizing time.The photoluminescence (PL) properties of the fabricated PAA films were measured. And the results show that a blue PL band occurs at the wavelength of 460nm. Another subsidiary peak moves from 480 to 530nm along with the increase of the anodizing voltage. At the same time, the intensity decreases and the full width at half maximum increases with the increasing of the anodizing voltage. Combining with the structure of PAA, we investigated the changes of the PL. The difference of the PL on the PAA prepared in oxalic and sulfuric electrolyte were discussed.The silver nanowires arrays with 20-100nm diameter were simply fabricated in the PAA templates by chemical deposition. The results of TEM and EDS show that the silver nanowires obtained were of high purity.