Fabrication of ultra thin porous alumina membrane on silicon substrate

Details of the fabrication of an ultra thin porous alumina membrane (PAM) on silicon substrate with controllable height (thinner than 100 nm) by a two-step anodization of the aluminum deposited on the silicon substrate in oxalic acid solution were revealed. A formation mechanism of preferential anodizing of the remaining aluminum islands in the Al/Si interface was firstly proposed on the basis of the current-time curve. FE-SEM top view and cross section micrographs showed that the non-ordered surface layer formed in the first anodizing process was etched away, and in the second process the hexagonal ordered arrangement of pores existed in the local domain, suggesting that the ultra thin porous alumina membrane can be used as template for further fabricating nano-devices and nano-structures on silicon substrate.