Fabrication And Optical Properties Of Porous AAO And Ordered Co/AAO Nano-array Structures

This dissertation, after summarized the latest development on fabrication and characterization of porous anodic aluminum oxide (AAO) and AAO nano-array structure, and mainly review achievements of prepared process and optical characterization of AAO films and nano-array structure, investigated the optical properties of porous AAO and ordered Co/AAO nano-array structures. The main conclusions and contents of researching are as follow:1. It was further optimized the technical process of order AAO, which prepared in oxalic acid, sulfuric acid and oxalic acid /sulfuric mixture acid. We can easily modulate the structural parameter of AAO templates, such as pore diameter, depth and density, within a larger range by changing the technical conditions including electrolyte type, concentration, temperature, oxidation voltage, current and time.2. We investigated the photoluminescence (PL) properties of AAO samples, which showed a strong optical band of 350～600nm, prepared in oxalic acid. The PL relative peak intensity of AAO template was modulated by oxide conditions and peak position was not change. The analysis revealed that the luminescence of AAO template prepared in oxalic acid solutions originated from F~+ centers and related to oxalate ions.3. The properties of AAO template, which prepared in oxalic/sulfuric mixture acid, were investigated. Firstly discovering that the PL peak of AAO films was sharply blueshift with the sulfuric acid concentrations increase in mixture electrolyte, which value was gradually decrease with increasing the sulfuric acid concentrations in mixture electrolyte , and the maximum blueshift was 65nm relative to the PL peak of AAO films prepared in oxalic acid. But the PL peak of AAO films was invariable with the oxalic acid concentrations change in mixture electrolyte. This further shows that the PL intensity of AAO membrane is source of PL centers which could be being transformed from the oxalic impurities in the AAO membranes during the anodization processes, and the sulfuric ion have influence on the PL intensity and peak of AAO membranes.4. The PL and photoabsorption of AAO template and Co/AAO nano-array structures were investigated. The results showed that the PL peak position of Co/AAO order nano-array structure and AAO template was the same, where were 395nm. The PL intensity of Co/AAO order nano-array structure dramatically decrease and its absorption edge showed dramatically redshift from near ultraviolet to infrared with the increasing amount of Co nanoparticles deposited in AAO template. The absorption bandedge redshifts were discussed in terms of Rayleigh scattering. The intensity decrease was caused by nonradiation energy transfer and transform between Co nanopticles and AAO template or metal nanoparticles absorb photon.