For the growth of the AAO film, we face a different situation when we reach the interface of the two-step sputtering process. There are Linsitinib mw defects Selleckchem Pevonedistat and little voids at the interface layer. Owing to the high current density, a new growth point is formed and new branches stretch out. As a result, ‘Y’ branches appear in the middle of the specimens. Figure 3 Cross-sectional images of sample and high-field anodic alumina films with different anodizing times. High-field anodic alumina films: (a) t

= 30 s, (b) t = 90 s, and (c) t = 150 s. Sample: (d) t = 40; this sample is sputtered in two steps. Figure 4 shows the top and bottom views of AAO after the pore widening process. In this process, a further attempt to broaden the range of pore diameters and lengths was obtained for AAO films on ITO. The FESEM images of Figure 4a,b show the aluminum films anodized in phosphoric acid and pore widening for 20 min. And the FESEM images

of Figure 4c,d show the aluminum films anodized in phosphoric acid and pore widening for 30 min. Figure 4a,c shows top views, while Figure 4b,d shows bottom views. All samples showed randomly distributed nanopores with irregular shapes and sizes. After pore widening, the pores can be observed more clearly. The pores in Figure 4a are smaller than those in Figure 4c. A barrier layer still exists in Figure 4b, while in Figure 4d, the barrier layer has been removed. This illustrates that as pore widening time increases, the pores are enlarged and opened. Figure 4 SEM images of AAO films anodized in high field CHIR-99021 mouse after pore widening. Pore widening for 20 min: (a) top and (b) bottom views. Pore widening for 30 min: (c) top and Tariquidar (d) bottom views. Anodization in oxalic acid Current density as a function of anodizing time is shown in Figure 5. The five curves are specimens anodized for different times and the specimens are Al sputtered on ITO glass for 1 h in one step and all the five curves share the same characteristics. It decreased rapidly first and then rose to the value ca. 4 mA/cm2. After keeping to this value for a long time, the current density had swings.

Finally, the current densities drop to a fixed value of about 3 mA/cm2, till the process ended. The process before 2,000 s can be explained as Figure 1. It is the swings that makes it different from the former process. These swings generated when the barrier layer reach the bottom of Al and touch the glass, which can be determined from cross-sectional images shown in Figure 6. As the top of the barrier layer reached the ITO glass substrate, the continuous Al film transformed into the Al pyramids between the pores. Different from the conditions of the high electric field, the low electric field would demand much more time in consuming the remaining Al pyramids. Therefore, there would be some inhomogeneity regions since the initial surface of Al was uneven. When the barrier layer in some regions opened up, the current density surged.