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International Journal of Spectroscopy
Volume 2015 (2015), Article ID 431678, 7 pages
Research Article

EPR Spectroscopy of Different Sol Concentration Synthesized Nanocrystalline-ZnO Thin Films

1CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India
2Department of Physics, Jamia Millia Islamia, New Delhi 110025, India
3Department of Electronics, Post Graduate College Bemina, Srinagar 190018, India

Received 30 June 2015; Revised 16 September 2015; Accepted 26 October 2015

Academic Editor: Kam-Sing Wong

Copyright © 2015 Manju Arora et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Nanocrystalline zinc oxide (nc-ZnO) thin films were grown on p-type silicon substrate through spin coating by sol-gel process using different sol concentrations (10 wt.%, 15 wt.%, and 25 wt.%). These films were characterized by high resolution nondestructive X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS) attachment, and electron paramagnetic resonance (EPR) techniques to understand variations in structural, morphological, and oxygen vacancy with respect to sol concentration. The film surface morphology changes from nanowall to nanorods on increasing sol concentration. EPR spectra revealed the systematic variation from ferromagnetic to paramagnetic nature in these nc-ZnO films. The broad EPR resonance signal arising from the strong dipolar-dipolar interactions among impurity defects present in nc-ZnO film deposited from 10 wt.% sol has been observed and a single strong narrow resonance signal pertaining to oxygen vacancies is obtained in 25 wt.% sol derived nc-ZnO film. The concentrations of impurity defects and oxygen vacancies are evaluated from EPR spectra, necessary for efficient optoelectronic devices development.