Nanowire Formation by Electrodeposition in Modified Nanoporous Polycrystalline Anodic Alumina Templates
- PDF / 1,046,066 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 39 Downloads / 185 Views
Nanowire formation by electrodeposition in modified nanoporous polycrystalline anodic alumina templates. M. Mikhaylova, M. Toprak, D. K. Kim, Y. Zhang, M. Muhammed. Materials Chemistry Division, Royal Institute of Technology, SE-100 44 Stockholm, Sweden ABSTRACT Template-assisted metallic nanowires, or hollow nanotubes, were synthesized by controlled electrodeposition of a metal salt under a controlled ac frequency in an anodic alumina membrane (AAM). Homogeneous large dimension AAM (D=5cm) was prepared by a modified two step anodization, using a specially designed reaction vessel that holds the sample perpendicular during the anodization. A ripping process, i.e. applying an opposite current after the anodization, easily separated the AAM from the Al substrate. TEM, SEM, and AFM were used to investigate the AAM structure, pore density and size, and distribution. Large aspect ratio metallic nanoparticles were prepared in an AAM within hexagonally close packed (hcp) alumina nanochannels. INTRODUCTION Fabrication of quasi-one–dimensional nanostructural materials has drawn increased attention in materials science for diverse applications in the fields of electronics, optics, magnetic, and energy storage [1]. There are several approaches to prepare large arrays of nanostructures, for example, by lithographic techniques such as electron beam lithography and ion beam lithography. Compared to these techniques, electrodeposition of nanoscale materials in the pores of a selfordered nanochannel matrix is of relatively low cost. Furthermore, electrodeposition is a fast process for the fabrication of large arrays of nanostructures with a very large aspect ratio, which is not possible with standard lithographic techniques. In recent years, anodic alumina synthesized by chemical methods is used as a template for producing isolated nanoporous films. AAM films grown in strong acid electrolytes form quite regular and highly anisotropic porous structures with diameters (dp) ranging from 10 to 200 nm, pore length (lp) from 1 to 50 µm, and pore density in the range 109-1011 cm-2[2]. Nanotubes, nanofibrils composed of metals, semiconductors, polymers, and various combinations of these materials have been reported using this AAM as a template [3]. In this study, the preparation of a rather large scale AAM as well as metallic nanowires, or nanotubes, growth using controlled pulse electrodeposition in the AAM is presented. A specially designed sample holder was used for the uniform anodization of aluminum substrate to avoid selective attack on the metal surface. Also, an electrochemical ripping process is introduced to separate the alumina membrane film from the aluminum substrate without damaging AAM. The resulting membrane possessed a hexagonal array of pores with controllable diameter and length, with a narrow pore size distribution. In-situ formed metallic nanowires are prepared in the AAM through a computer controlled pulse deposition process. In the case of template assisted synthesis, the diameter of the nanoparticles is confined wit
Data Loading...
