Structural evolution of self-ordered alumina tapered nanopores with 100 nm interpore distance

Advisor : Cheng-Hsin Chuang Advisee Po-Hsiang Wang﹕

Date 2013/04/12﹕

Paper Survey

Juan Li a,b,c, Congshan Li a,c, Xuefeng Gaoa,∗a Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, PR China

b Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, PR Chinac Graduate University of the Chinese Academy of Sciences, Beijing 100049, PR China

Applied Surface Science 257 (2011) 10390– 10394

OutlinePaper Survey

• Experimental

• Result and discussion

Future Works

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Experimental

Fig. 1. SEM top-views (left) and side-views (right) of the as-prepared PAA nanostructures. With the cyclic times increasing, the pore structure is gradually evolved into the parabola-shaped (a), the trumpet-shaped (b) and cone-shaped (c), and more complex geometry such as the cone-shaped (d), pencil-shaped (e) and U-shaped (f) pores with tiny nipples at the top of cell joints.

1st anodization: 40V , 8hr, 17 , 0.3M Oxalic acid.℃ removal the oxide layer: 3hr, Chromic resoluction.2nd anodization: 20sec, Widening time: 8min

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Results and discussion

Fig. 2. (a) Current density (j)–time (t) transients under the varied cyclic action from the 1st to 13th times. (b) The thickness (TT-BL) of barrier layer and the thickness (TT-P) of taper-pores as a function of the cyclic times of multi-step anodizing and etching. (c) The thickness (TC-BL) of the barrier layer and the thickness (TC-P) of cylindrical pores as a function of the cyclic times of multi-step anodizing without inserted etching.

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Results and discussion

Fig. 3. (a) Schematic depiction of the top morphologies of pores adorned with nipples at the cell joints. As the anion-doped part (gray) was dissolved out, the open sizes of pores reached their limit. With the etching duration extending, the cell boundary (black) was further dissolved out while the cell joints (nipples) were remained. (b) The open size of pores varied with the cyclic times

Fig. 4. Top-view (left) and side-view (right) SEM images of the cone-shaped PAA nanostructures varied with etching time: (a) 5 min; (b) 15 min; (c) 25 min.

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Results and discussion

Fig. 5. Side-view SEM images of conical PAA nanostructures with tunable aspect ratios (AR), which were obtained under different cyclic anodization time. (a) AR = 1.4 (10 s); (b) AR = 1.9 (15 s); (c) AR = 3.3 (30 s); (d) AR = 4.6 (40 s); (e) AR = 7.0 (60 s) and (f) AR = 10.4 (80 s). (g) The curve of the aspect ratio of cone-shaped nanopores linearly varied with the anodization time.

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Future Works

Paper survey

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