(c,d) Cross-sectional view at low and high magnification. Figure 3 check details Schematic diagram for co-deposition process of Co-Ni binary nanowires in nanopores of AAO template. (a) AAO template with circular shape, (b) filling of nanopores started from Co-Ni binary nanowires at the bottom of AAO by exposing circular
area to the Co and Ni precursor solution, (c) complete filling of the alumina nanopores from Co-Ni binary nanowires, (d) dissolution of alumina in C188-9 cost NaOH to get Co-Ni binary nanowires. Metallic cobalt and nickel give an intermetallic phase according to the following reaction : (3) It is important to mention that deposition of metal precursors started in the nanopores of AAO only when the polarity of the electrodes is reversed unlike anodization. The electrodeposition process was continued
until the nanopores are filled completely with Co-Ni materials (Figure 3c). It is worth noticing that the deposition time must be controlled to suppress the outer grow of depositing material from the AAO template and subsequent cap formation [30, 31]. Such bottom-up growth process fills all the nanochannels of AAO with Co-Ni material, resulting in the formation of Co-Ni binary nanowires (Figure 4). Finally Co-Ni binary nanowires were liberated by dissolving the AAO template (Figure 3d). The morphology of Co-Ni binary nanowires is shown in Figure 4. Figure 4a shows SEM image of the top surface of Co-Ni binary nanowires embedded in AAO template. It can be seen from the image that the nanopores of AAO template are find more filled completely with Co-Ni binary nanowires showing the uniform deposition and homogeneity of the nanowires by AC electrodepsoition. It clearly shows that the growth of Co-Ni binary nanowires was restricted into the nanopores of AAO and suppressed the subsequent cape formation at the top. Figure 4b shows the cross-sectional image of Co-Ni binary nanowires embedded in the alumina template giving a bright contrast as marked by arrows. Few nanochannels without Co-Ni binary nanowires can also be seen in the image. This indicates that some Co-Ni binary nanowires have been broken and removed from the AAO template.
Breaking and removal of Co-Ni binary nanowires from the alumina nanochannels is pheromone attributed to the mechanical stress applied during the preparation of sample for cross-sectional view in SEM. Since the sample was simply cut with scissor, the empty alumina nanochannels might indicate that Co-Ni binary nanowires were embedded in the other half portion of the alumina template. Moreover, the image verifies that the deposition of Co-Ni binary nanowires start from the bottom surface of alumina nanochannels as explained in the Figure 3b. The marked area near the Al substrates (Figure 4b) represents the bottom part of the Co-Ni binary nanowires which confirm the deposition without the modification of the barrier layer. Figure 4c,d shows the top surface view of Co-Ni binary nanowires after partial dissolution of AAO template.