Surface characterization study of nanoporous anodic aluminium oxide thin film synthesized by single-step anodization

Nanoporous anodic aluminium oxide (AAO) thin film electrodes were prepared by using a single step anodization method in 0.3 M oxalic acid at 40 V for 1 h. Electrolyte temperature was controlled and maintained at 15 °C by using ice water bath. After anodized, AAO surfaces were etched by using 5% phosphoric acid (H3PO4) solution at 30 °C to remove the AAO top rough surfaces and widening the pores. Effect of different etching duration to the pore widening was investigated at 10, 20 and 30 minutes, respectively. Regularity of the pores arrangements before and after etching were analysed by fast fourier transform (FFT) profile images that were generated from FESEM images. From observation, well ordered nanoporous structures were successfully revealed after top rough surfaces were removed by etching. Pores sizes were also found to be increased with the increasing of etching duration. Further investigations were done by x-ray diffraction (XRD) analysis and fourier transform infra-red spectroscopy (FTIR) to characterize and find out the crystallinity properties and functionalities of AAO thin film electrode surfaces.