Defects in three-dimensional spherical assemblies of Ni-doped ZnO nanocrystals
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ensional spherical assemblies of Nidoped ZnO nanocrystals K.C. Barick, M. Aslam, Jinsong Wu, Vinayak P. Dravid and D. Bahadur Journal of Materials Research / Volume 24 / Issue 12 / 2009, pp 3543 3550 DOI: 10.1557/jmr.2009.0446
Link to this article: http://journals.cambridge.org/abstract_S0884291400035329 How to cite this article: K.C. Barick, M. Aslam, Jinsong Wu, Vinayak P. Dravid and D. Bahadur (2009). Defects in threedimensional spherical assemblies of Nidoped ZnO nanocrystals. Journal of Materials Research,24, pp 35433550 doi:10.1557/jmr.2009.0446 Request Permissions : Click here
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Defects in three-dimensional spherical assemblies of Ni-doped ZnO nanocrystals Kanhu Charan Barick Department of Metallurgical Engineering & Materials Science, Indian Institute of Technology Bombay, Mumbai-400076, India
Mohammed Aslam Department of Physics, Indian Institute of Technology Bombay, Mumbai-400076, India
Jinsong Wu and Vinayak P. Dravida) Department of Materials Science & Engineering, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208
Dhirendra Bahadurb) Department of Metallurgical Engineering & Materials Science, Indian Institute of Technology Bombay, Mumbai-400076, India (Received 10 May 2009; accepted 18 August 2009)
Three-dimensional spherical assemblies of Ni-doped ZnO nanocrystals have been prepared by the solution phase synthesis process. It has been observed that transition metal ions (Zn, Ni) are uniformly distributed in the sample and exist in the +2 oxidation state. Detailed investigation of structural defects formed during the formation of spherical assemblies by oriented attachment of nanocrystals was carried out by high-resolution transmission electron microscope (HRTEM), Raman and photoluminescence (PL) spectroscopy. HRTEM analysis revealed the existence of various crystal defects, such as stacking faults, dislocations, etc. The incorporation of Ni2+ into ZnO structure strongly influences the vibrational and optical properties of the sample due to the increment of defect densities. Compared to the optical phonons of ZnO, an additional mode observed at 538 cm1 in Raman spectra of Ni-doped ZnO could be associated with the incorporation of Ni2+ in Zn2+ site. The increase in PL intensity of green emission with Ni2+ doping indicates the formation of a higher concentration of oxygen vacancy in doped nanostructures. I. INTRODUCTION
ZnO nanocrystals have been the subject of intense research because of their extraordinary electrical and optical properties at the nanoscale, which make them promising candidates for various applications.1–4 Furthermore, ZnO has been predicated to be ferromagnetic with a Curie point above room temperature by doping with Mn, Co, or Ni.5–7 The dopants, introduced into the ZnO nanocrystals, can modulate the local structure and cause the dramatic changes of physical properties caused by the quantum confinement effect.8,9 The scattering of e
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