Co-DOPED ZnO NANOWIRES GROWN BY VAPOR { LIQUID { SOLID METHOD: STRUCTURAL, OPTICAL AND MAGNETIC STUDIES BAPPADITYA PAL and SOUMEN DHARA Department of Physics, Indian Institute of Technology Guwahati Guwahati-781 039, India P. K. GIRI Department of Physics and Centre for Nanotechnology Indian Institute of Technology Guwahati, Guwahati-781 039, India giri@iitg.ernet.in Received 17 April 2012 Accepted 19 June 2012 Published We report on the growth of Co-doped ZnO nanowires (NWs) on Si substrate using a self-catalytic vapor deposition method from a Co-doped ZnO nanopowder source and study its structural, optical and magnetic properties for the as-grown and rapid thermal annealed samples. Co (5%)-doped ZnO (ZnCoO) nanoparticles (NPs) are used as source material for the growth process. Electron mi- croscopy imaging clearly reveals the formation of long ZnO NWs with uniform diameter. X-ray di®raction analysis con¯rms the single crystalline hexagonal structure of Co-doped ZnO NWs without impurities of metallic cobalt or other phases. Micro-Raman studies of doped samples show doping/disorder induced additional modes as compared to the undoped ZnO. Room temperature photoluminescence spectra of the doped ZnO NWs show strong emission band at 380 nm and no signi¯cant emission was observed in the visible region indicating low defect content in the NWs. The ¯eld dependent magnetization (MH curve) measured at room temperature exhibits paramagnetic nature for the NWs with the magnetic moment in the range 23.7 milli-emu/cm 2 for the applied ¯eld of 2 Tesla, while the source ZnCoO NPs exhibit room temperature ferromagnetism with saturation magnetization 6 emu/g. Possible mechanism of alteration in magnetic behavior in doped NWs are discussed based on the growth conditions and role of defects. Keywords : ZnO nanowire; doping; ferromagnetism; photoluminescence. 1. Introduction In recent years, considerable research e®orts have been focused on ZnO-based dilute magnetic semi- conductors 13 due to the prediction of possible ferromagnetic properties with Curie temperature (T C ) above room temperature. 4 In particular, ZnO- based materials have been receiving considerable attention due to its abundance and environment- friendly nature and also due to its potential as a suitable optoelectronic material with a wide band 1250028-1 September 24, 2012 6:10:40pm WSPC/213-NANO 1250028 ISSN: 1793-2920 4rd Reading NANO: Brief Reports and Reviews Vol. 7, No. 4 (2012) 1250028 (8 pages) © World Scienti¯c Publishing Company DOI: 10.1142/S1793292012500282