Ordered and parallel niobium oxide nano-tubes fabricated using Atomic Layer Deposition in anodic alumina templates
- PDF / 724,906 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 88 Downloads / 202 Views
0901-Ra24-05.1
Ordered and parallel niobium oxide nano-tubes fabricated using Atomic Layer Deposition in anodic alumina templates Mårten Rooth, Anders Johansson, Mats Boman and Anders Hårsta Department of Materials Chemistry The Ångström Laboratory, Uppsala University Box 531, SE-75121 Uppsala, Sweden ABSTRACT Amorphous niobium oxide (Nb2O5) nano-tubes were fabricated inside anodic alumina templates using atomic layer deposition (ALD). The nanoporous templates were in-house fabricated anodic alumina membranes having an inter-pore distance of about 100 nm with pores lengths of 2 µm. The pores were parallel and well ordered in a hexagonal pattern. Atomic layer deposition was performed using gas pulses of niobium iodide (NbI5) and oxygen separated by purging pulses of argon. By employing long gas pulses (30 s) it was possible to get coherent and amorphous Nb2O5 films conformally covering the pore-walls of the alumina template. The outer diameter of the nano-tubes was tailored between 40 and 80 nm by using alumina templates with different pore sizes. By using template membranes with pores not opened in the bottom, nanotubes with one side closed could be fabricated. Free-standing, and still parallel, nano-tubes could be obtained by selectively etching away the alumina template using phosphoric acid. Using the above mentioned procedure it was possible to fabricate unsurpassed parallel niobium oxide nanotubes of equal length, diameter and wall-thickness, ordered in a perfect hexagonal pattern. The samples were analysed using high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), electron diffraction and x-ray fluorescence spectroscopy (XRFS). INTRODUCTION The last decades increasing interest for nanostructures has called for new and better synthesis methods. One particular interesting field in the world of nanoscience is the nanotube area. The most famous nanotubular system is by far the one based on carbon and the synthesis of carbon nanotubes, first described by Iijima [1] in 1991. In order to obtain ordered nanotubular systems in other materials a variety of methods have been used. C60 on surfaces has been used as growth promotors for synthesis of MoS2 and WS2 nanotubes [2] and a common approach to achieve ordered arrays of nano-tubes is the usage of a well-ordered porous material as template for thin film deposition. Porous metal oxides, in particular anodic alumina membranes, have successfully been used for that purpose; e. g., silver nano-tubes have been produced using thermal decomposition of silver nitrate [3], Prussian blue nano-tubes have been fabricated by sequential wet chemical methods [4] and various oxides and metals have been deposited on the pore walls using sol-gel techniques and ALD [5, 6]. Nb2O5 is a material of large interest in both scientific and industrial fields; it is a wide band gap dielectric material with a high refractive index that is reported to exhibit both electrochromism [7] and catalytic activity [8, 9]. These properties offers us a number of inte
Data Loading...
