Abstract
High-purity aluminum thin films (500 nm thick) were anodized in a mixture of phosphoric acid and lithium phosphate monobasic at a constant anodizing voltage (2.5 or 50 V) to obtain different structures of porous alumina doped with lithium ions. The morphology of the formed porous alumina was obtained by scanning electron microscopy (SEM). A few characteristic parameters of porous alumina such as pore diameter, inter-pore distance, volume expansion and etching process were investigated. The results showed that porous alumina having irregular, high pore size and very thin walls were formed at low anodization voltage (2.5 V). The resulting low anodizing rates also lead to the dissolution of alumina in the electrolyte. In contrast, conventional pore structures with volume expansion factor close to 1.4 were formed at high anodization voltage (50 V). The presence of lithium in porous anodic alumina confirmed by Raman spectroscopy. The possible formation of porous alumina incorporated with lithium ions opens the way for various applications such as energy and sensor based on anodized Al as a matrix of the Li-composite electrolyte.