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 , PR China b Institute of Biophysics, Chinese Academy of Sciences, Beijing , PR China c Graduate University of the Chinese Academy of Sciences, Beijing , PR China Applied Surface Science 257 (2011) 10390– 10394

Outline  Paper Survey Experimental Result and discussion  Future Works 2

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

4 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.

5 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.

6 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.

7 Future Works  Paper survey  微系統 paper

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