Effects of ethanol in oxalic acid on the synthesis of porous anodic alumina

Porous anodic alumina is a self-organizing porous material suitable as a template for obtaining nanostructured semiconductor materials. However, low temperature is generally used for the synthesis of porous anodic alumina. In this study, porous anodic alumina films were synthesized by a simple one-step anodizing technique at constant potential 40V using different volume percentage of ethanol in 0.5M oxalic acid at the temperatures of 25 °C. The current versus time transient was recorded by using Keithley sourcemeter. The morphology of the samples was viewed by a scanning electron microscopy. The current versus time transient decreased with the volume percent of ethanol, indicating reduction of growth rate of porous anodic alumina. Porous anodic alumina formed in oxalic acid without ethanol exhibit a complicated structure with irregular pore size and pore shape. Increasing volume percent of ethanol in the oxalic acid improved the pore size and shape. This is probably due to the cooling effect of the ethanol and prolonged time for pore organization. Typical morphology of porous anodic alumina can be formed by anodizing at 40 V at room temperature of 25 °C in 0.5 M oxalic acid with the addition of minimum of 30 volume percent of ethanol.