The electrochemical deposition of nanostructured cobalt films from lyotropic liquid crystalline media

Lyotropic liquid crystalline phases formed at high concentrations of nonion ic surfactants provide a versatile templating medium that can be used to pr oduce nanostructured materials with regular arrays of pores of nanometer di mension and extended periodicity. In this work, we have used this technique to prepare nanostructured cobalt films on gold substrates by electrochemic al deposition of cobalt from cobalt acetate dissolved in the aqueous domain s of the hexagonal lyotropic liquid crystalline phase of Brij 56(C16EO10). Low angle X-ray and transmission electron microscope studies show that the resulting cobalt films have a regular nanostructure consisting of a hexagon al array of cylindrical pores. The repeat distance for this nanostructure l ies in the range of 7-11 nm and can be systematically varied by varying the amount of n-heptane added to the template mixture. Preliminary magnetic me asurements on the nanostructured samples suggest that the coercivity (H-c) of these cobalt films is three to five times greater than that for polycrys talline cobalt and that it varies systematically with the size of the pores . (C) 2001 The Electrochemical Society. All rights reserved.