Figure 6

Cross-sectional SEM images of two samples. One non-annealed and one that was annealed in nitrogen gas before anodization. Cross-sectional view of sample 1 that was not annealed (images 1 of (a) and (b)) and sample 2 that was annealed at 500°C for 30 min in nitrogen gas before anodization for alumina formation (annealed; images 2 of (a) and (b)). Etching was performed for 20 s in SF₆ (images 1 and 2 in (a)) and SF₆/CHF₃ (images 1 and 2 in (b)), respectively.