Electrodeposition of Nanowire in mesoporous silica thin films
Martin G. Bakker, Roger Campbell and Ravi Sekhon
Mesoporous silica templated by surfactants or block co-polymers has pores in the 3-5 nm range. We have prepared such films on copper coated silicon wafers by dip coating. The template is then removed by washing with isopropanol leaving empty pores. XRD has been used to establish the periodic nature of the pores, and Variable Angle Spectroscopic Ellipsometry on comparable samples grown in the absence of the copper underlayer, shows a film thickness of ca. 380 nm with 46% void volume. Cobalt and nickel have been electrodeposited into the film. Scanning SEM/EDAX shows growth of cobalt through the film. The absence of cracks at the micron scale rules out cobalt growth through such cracks. High resolution SEM shows the growth of 40 nm scale nickel islands on the top surface of the film, clear indication that growth is occurring through the silica film to give 3-5 nm diameter nanowires of cobalt and nickel. We are currently preparing samples for TEM to image the nanowires and are beginning MOKE measurements to characterize their magnetic properties.