Self-organized high aspect ratio porous hafnium oxide prepared by electrochemical anodization

We report on the fabrication of self-organized porous hafnium oxide layers by anodization of hafnium in H2SO4 electrolytes containing NaF. The results show that porous hafnium oxide layers can be formed under a range of experimental conditions. A key factor affecting the morphology and the structure of porous oxide is the anodization potential. Using optimized anodization conditions, highly ordered tube-like porous structures can be formed. The pore diameter increases with increasing potential from approximately 15 to 90 nm. The porous oxide layers can be grown to thickness of several tens micrometer and therefore possess aspect ratios comparable to the best self-organizing systems reported previously in the literature.