Template-based synthesis of single- and multi-layered metal oxide nanotubes using ALD
Uppsala University, Department of Materials Chemistry, Angstrom Laboratory, Uppsala, Sweden
A very interesting field within the world of nanoscience is the nanotube area. One route to obtain well-ordered arrays of nanotubes is to use a template and transfer the pattern to a desired material. A suitable template for this method is anodic aluminium oxide (AAO), which can be electrochemically grown and exhibits a high degree of order over large areas. A problem is that few deposition techniques are able to conformally cover the pore-walls of the AAO. However, ALD is a very well suited technique for the template deposition method.In the present paper, different metal oxide nanotubes were manufactured by ALD using AAO templates, both commercial and in-house made. An overview of the obtained results will be presented for synthesis of single-layered Nb2O5, Fe2O3 and TiO2 nanotubes. In addition, some preliminary results for fabrication of multi-layered TiO2/Fe2O3 nanotubes will be briefly mentioned. The precursor combinations used were NbI5-O2, Fe(Cp)2-O2 and TiI4-H2O, with pulse lengths of 30 s for both precursors and purging pulses. These large values for the pulse lengths are necessary to reach saturation of the precursor species on the surface of the pore walls and also to suppress any possible gas phase reactions in the pores.
For all metal oxides, well-ordered and free-standing nanotubes with aspect ratios up to 35 could be fabricated in the in-house made AAO templates. In commercial templates, aspect ratios of 200 was achieved. From SEM and TEM studies it could be seen that the pore-walls of the AAO were conformally covered, with the same oxide thickness regardless of the depth. This indicates that the duration of the pulses were sufficient to saturate the entire surface of the pore walls.
Presentation: Invited at E-MRS Fall Meeting 2007, Symposium C, by Anders Hårsta
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-11 13:51 Revised: 2009-06-07 00:44