Preparation of cobalt nanowires in porous aluminum oxide: Study of the effect of barrier layer
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Saeid Soltaniana) Department of Physics, University of Kurdistan, Sanandaj, 66177-15175 Iran
Habibollah Danyali Department of Electrical Engineering, University of Kurdistan, Sanandaj, 66177-15175 Iran
Rahman Hallaj and Abdollah Salimi Department of Chemistry, University of Kurdistan, Sanandaj, 66177-15175 Iran
Seyed Mohammad Elahi Department of Physics, Science and Research Branch, Islamic Azad University, Tehran 775-14515, Iran
Peyman Servati Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, V6T1Z4 Canada (Received 3 January 2012; accepted 1 June 2012)
High-density cobalt (Co) nanowires (NWs) were fabricated using porous anodized aluminum oxide as a template. Measurement results show a high magnetic performance for NWs with a coercivity of about 1750 Oe and strong magnetic anisotropy with an easy axis parallel to the NW direction. We have investigated the effect of alternating current (AC) electrodeposition frequency on the magnetic properties of NW samples. We show that understanding the effect of barrier layer is critical for controlling the rate of NW electrodeposition. A circuit model is proposed that accurately describes the role of the barrier and interfacial layers during deposition. Results obtained by simulation of the circuit show an excellent agreement with experimental results for different frequencies and voltages. It is shown that the amount of electrodeposited material can be estimated based on the difference between the anodic and cathodic half cycles in the electrodeposited current. Use of higher frequency leads to more symmetrical half cycles and smaller electrodeposited material.
I. INTRODUCTION
Fabrication of inorganic nanowires (NWs) with controlled morphology has attracted a lot of interest due to their potential applications in high-density storage media,1 highly sensitive giant magnetoresistance (GMR) materials,2,3 sensors,4–6 biosensors,7 photocatalysts,8,9 thermoelectric cooling systems,10 and photonic crystals.11–13 Among different deposition methods, template-assisted techniques are promising due to the high level control over morphology and packing density of NWs. Polycarbonate films as well as anodized aluminum oxide (AAO) are the most popular templates which have been used.14–18 AAO is preferred in comparison with polycarbonate templates because of its potential for high-density storage applications. AAO templates with parallel cylindrical pores in the form of Address all correspondence to this author. a) e-mail: [email protected]; [email protected] Present address: Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, V6T1Z4 Canada DOI: 10.1557/jmr.2012.198
hexagonally close-packed patterns have been demonstrated, using a two-step anodization process developed by Masuda et al.19–21 The anodization of aluminum in certain electrolytes results in the following structure for the AAO template: aluminum base, alumina barrier layer separating the aluminum from the nanoporous membrane, and the nanop
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