Zhou et al. Nanoscale Research Letters 2011, 6:276 http://www.nanoscalereslett.com/content/6/1/276 kinds: metallic matrices (Cu, Ag and Nb) [35-38]; cera- mic matrices (Al2O3 and AlN) [5,23,39]; and polymeric matrices [22,24]. In this article, we report on the electro- chemical deposition of Co into n-type porous InP semi- conductor matrix based on organic solution of cobalt chloride, where the organic solution, i.e., ethanol solu- tion, was applied to protect Co from oxidization. The structure and magnetic properties of such Co/InP nano- composites were also investigated. Experiment details Co/InP magnetic semiconductor nanocomposites were fabricated by one-step electrodeposition of Co particles onto n-type porous InP templates. Figure 1 shows the schematic illustration of the fabrication of Co/InP com- posite structure. First, the n-type porous InP template was prepared by a two-step etching method [40]. The starting material was Sn-doped InP (>1 × 1018 cm-3) wafer, which was first etched at a constant voltage of 8 V in 7.5% HCl aqueous solution for 30 s. Next, the speci- men was immersed in a mixture of pure HCl and H3PO4 (HCl:H3PO4 = 1:3 v/v) for a few minutes to remove the top irregular layer to obtain n-type porous InP templates with uniform and square pore arrays. This was followed by electrochemical deposition of Co particles onto por- ous InP templates, performed using a three-electrode cell, employing a porous InP template as the working electrode and a graphite plate counter-electrode. The reference electrode was a saturated calomel electrode (SCE), isolated from the solution by a salt bridge. The deposition bath was 0.1 M/L CoCl2 ethanol solution, pre- pared by dissolving CoCl2 in ethanol. Before the deposi- tion of Co, the porous InP template was immersed in the bath about 1 h to allow the solution completely wet the inner pore walls. The applied potential was kept at 2.0 V with respect to SCE. After the deposition of Co, the sam- ple was cleaned by de-ionized water, dried in N2 atmo- sphere, and then kept in anhydrous ethanol. All the experiments were performed at room temperature. The morphology of Co/InP nanocomposite structures was subsequently studied by field-emission scanning electron microscope (FE-SEM). The composition and Page 2 of 6 crystallographic structure of samples were investigated by energy dispersive X-ray spectrometer (EDS) system attached to SEM and X-ray diffraction (XRD) with Cu Κa radiation (l = 1.54 Å). Physical property measure- ment system was applied to characterize magnetic prop- erties of such Co/InP nanocomposites at 300 K with magnetic field sweeping from -15 to 15 KOe. Results and discussions Structure characterization of Co/InP nanocomposites Figure 2a shows the typical FE-SEM image of n-type por- ous InP template with nearly uniform and square pore arrays. In order to study the growth process of Co in por- ous InP semiconductor matrix, Co/InP nanocomposites with different deposition times were prepared. The cross- sectional morphologies of different samples are shown in Figure 2b, c, d. There is almost no Co in the inner channel wall of the InP matrix when the deposition time is 30 s, as shown in Figure 2b. When the deposition time increases to 90 s, it was found that a small amount of Co nanoparti- cles uniformly distribute on the whole inner channel walls of the InP template (Figure 2c). On further increasing the deposition time, the needle-shaped Co forms on the inner pore walls of InP as shown in Figure 2d. It is noted that Co particles prefer to uniformly distribute over the chan- nel wall surface of the InP template than gather at the bot- tom of channel, which may result from conductivity of n-type porous InP template. In other words, the deposition of metallic Co particles may occur at any position of the pore sidewall surface of InP template (as shown by the schematic of Figure 1), which is different from the “bot- tom-up” growth mechanism in the insulation templates, such as AAO. Since the channel walls of the insulation templates are stable and nonconductive in the solution, the growth by electrodeposition is always from the bottom to the opening when a conductive layer is fabricated at the bottom side of the insulation channels [9]. Therefore, adjustable electrodepositions may be realized by tuning the conductivity and reactivity of such porous InP matrix, which may open up a new branch in the fabrication of nanocomposite materials. A detailed discussion for this is not given here because it is not the main concern for this Figure 1 Schematic of fabrication process of Co/InP nanocomposite structure.