Structural, Optical and Magnetic properties of Co-doped ZnO Nanopowders
- PDF / 697,990 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 30 Downloads / 350 Views
Structural, Optical and Magnetic properties of Co-doped ZnO Nanopowders Segundo R. Jáuregui-Rosas1, Oscar J. Perales-Perez2, Lourdes A. Noriega3 and Luis A. Castillo3 1
Laboratorio de Física de Materiales, Departamento de Física, Universidad Nacional de Trujillo, Juan Pablo II Av. S/N, Trujillo - Peru. 2 Department of Engineering Science and Materials, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9044, USA 3 Escuela de Física, Universidad Nacional de Trujillo, Juan Pablo II Av. S/N, Trujillo - Peru. ABSTRACT Nanocrystalline Zn1-xCoxO powders exhibiting a preferential crystal growth along the (002) plane have been synthesized in the atomic fraction, ‘x’, range of 0.0-0.0625 by a wet chemical method. The effect of the dopant concentration on the corresponding structural, optical and magnetic properties was also evaluated. XRD analyses evidenced the development of singlephase wurtzite with no traces of any impurity for all the dopant levels. The higher intensity of the (002) peak, when compared to the XRD peaks in bulk ZnO, indicates the preferential crystal growth along the c-axis in hexagonal wurtzite cell. The linear dependence of cell parameters a and c with ‘x’ suggests the actual replacement of Zn by Co ions in the host oxide lattice. Micro Raman spectroscopy measurements showed a band centered at 535cm-1, which can be assigned to a local vibrational mode related to Co species in addition to the normal modes associated with wurtzite. The relative broadening of this band at 535cm-1 was enhanced by increasing ‘x’. The other characteristic bands of ZnO corresponding to A1 (E2, E1) and E2High modes were red shifted for all Co contents. UV-vis measurements showed that the energy band gap of as-synthesized nanopowders decreased with increasing Co2+ content up to x = 0.03 and increased for higher contents. Room-temperature magnetization measurements revealed the paramagnetic behavior of the Co-doped ZnO nanopowders. INTRODUCTION After theoretical predictions of room temperature ferromagnetism in transition metal (TM)-doped ZnO [1, 2], intensive theoretical and experimental work have been carried out with the aim of identifying and synthesize candidate materials for spintronic applications with practical ordering temperatures. Particularly, the Co-doped ZnO system has received remarkable attention and different particle morphologies have been proposed so far including nanorods [35], thin films [6] and nanoparticles [7,8]. Proposed syntheses routes based on PLD [6], hydrothermal [5], and sol-gel methods [7,8] are among the most reproducible. Despite of the intensive research work on this system, the experimental results are still controversial and suggests that room temperature magnetism in ZnO containing Co2+ ions will be strongly sensitive to the synthesis approach [9,10]. Nanostructures of ZnO oxide have also been proposed for photo-catalytic applications [11]; however, its wide band gap (3.37eV) lies in UV region that makes it inactive under visible light. One alternative to overcome this limitation is by d
Data Loading...
