Delivered by Ingenta to: Rice University, Fondren Library IP : 176.14.23.89 Fri, 27 Jul 2012 18:27:39 RESEARCH ARTICLE Copyright © 2012 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 12, 1386–1389, 2012 Structural and Magnetic Properties of Zn 1-x Co x O Nanorods Prepared by Microwave Irradiation Technique Faheem Ahmed, Shalendra Kumar, Nishat Arshi, M. S. Anwar, Bon Heun Koo, and Chan Gyu Lee ∗ School of Nano and Advanced Materials Engineering, Changwon National University, Changwon, Gyeongnam, 641-773, Korea We have successfully synthesized large-scale aggregative flowerlike Zn 1-x Co x O (00 ≤ x ≤ 007) nanostructures, consisting of many branches of nanorods at different orientations with diameter within 100–150 nm (tip diameter ∼ 50 nm) and length of ∼1 m. The rods were prepared using Zinc nitrate, cobalt nitrate and KOH in 180 Watt microwave radiation for short time interval. The synthe- sized nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM) and DC magneti- zation measurements. XRD and TEM results indicate that the novel flowerlike nanostructures are hexagonal with wurtzite structure and Co ions were successfully incorporated into the lattice posi- tion of Zn ions in ZnO matrix. The selected area electron diffraction (SAED) pattern reveals that the nanorods are single crystal in nature and preferentially grow along [0 0 1] direction. Magnetic studies show that Zn 1-x Co x O nanorods exhibit room temperature ferromagnetism. This novel nano- structure could be a promising candidate for a variety of future spintronic applications. Keywords: Microwave Irradiation, Nanorods, Diluted Magnetic Semiconductors, X-Ray Diffraction. 1. INTRODUCTION In recent years, ferromagnetism in diluted magnetic semi- conductors (DMSs) has attracted ever-increasing attention because of the potential use of both the charge and spin of electrons for spintronic devices. 1 From the applica- tion point of view, it is necessary that a DMSs material should be ferromagnetic at or above room temperature to be used in spintronic devices. Since the theoretical pre- diction of room temperature ferromagnetism (RTFM) on ZnO-based DMSs, 2 the investigation of transition metal doped ZnO, especially Co-doped ZnO, has been identified as a promising DMSs material. Generally, Co is one of the most effective dopant to tune both optical and mag- netic properties due to its abundant electron states as well as its very small influence on the ZnO lattice structure. Interestingly in these systems, the origin of ferromag- netism remains a subject of debate, and there is a great deal of controversy over the origin of ferromagnetism. On the other hand, developing one-dimensional (1D) DMSs materials are of great interest, for the reason that the 1D nanomaterials are perfect research systems for fabricating nanoscale field effect transistors, sensors, optoelectronic devices, logic circuits, and lasers. 3 Numerous techniques ∗ Author to whom correspondence should be addressed. have been conducted on the fabrication of pure and tran- sition metal (TM) doped ZnO nanomaterials. 4–7 However, it still desires a great deal of work to discover new simple approach with low cost to synthesize 1D ZnO nanomate- rials. In comparison to other approaches, solution method has its own advantages, such as low temperature, high pro- duction yield and high quality. Nowadays, a new method has been reported: microwave-assisted synthesis. Due to its unique features such as short reaction time, enhanced reac- tion selectivity, energy saving, and high reaction rate, 8 9 the application of microwave-assisted synthesis of ZnO nanomaterials has been rapidly increasing. 9–13 Co-doped ZnO nanopowders have been synthesized in various meth- ods, including a simple chemical method, 14 auto combus- tion method 15 and co-precipitation technique. 16 However, synthesis of Co doped ZnO nanorods using microwave irradiation technique has not been reported yet. In this paper, we present a simple microwave-assisted chemical method to fabricate Zn 1-x Co x O nanorods. We have pro- duced single phase Zn 1-x Co x O nanorods of flower like morphology and good crystalline quality. The nanorods were characterized by XRD, FESEM, HRTEM and mag- netization measurements. The synthesis method presented here also allows for the doping of different transition met- als (e.g., Mn, Fe, Cu); however, this paper is limited to the cobalt-doped system. 1386 J. Nanosci. Nanotechnol. 2012, Vol. 12, No. 2 1533-4880/2012/12/1386/004 doi:10.1166/jnn.2012.4631