title: Variation of nanopore diameter along porous anodic alumina channels by multi-step anodization.
abstract: In order to form tapered nanocapillaries, we investigated a method to vary the nanopore diameter along the porous anodic alumina (PAA) channels using multi-step anodization. By anodizing the aluminum in either single acid (H3PO4) or multi-acid (H2SO4, oxalic acid and H3PO4) with increasing or decreasing voltage, the diameter of the nanopore along the PAA channel can be varied systematically corresponding to the applied voltages. The pore size along the channel can be enlarged or shrunken in the range of 20 nm to 200 nm. Structural engineering of the template along the film growth direction can be achieved by deliberately designing a suitable voltage and electrolyte together with anodization time.
authors: School of Materials Science and Engineering, Nanyang Technological University, Singapore, 50 Nanyang Avenue, 639798 Singapore.
authors: Kwang Hong
authors: KH
authors: Lee
authors: Xin Yuan
authors: XY
authors: Lim
authors: Kah Wing
authors: KW
authors: Wai
authors: Filippo
authors: F
authors: Romanato
authors: Chee Cheong
authors: CC
authors: Wong