Please use this identifier to cite or link to this item: http://lib.jncasr.ac.in:8080/jspui/handle/10572/2467
Title: Probing optical band gaps at nanoscale from tetrahedral cation vacancy defects and variation of cation ordering in NiCo2O4 epitaxial thin films
Authors: Dileep, K.
Loukya, B.
Silwal, P.
Gupta, A.
Datta, Ranjan
Keywords: Applied Physics
Spinel Oxides
Hreels
Optical Band Gaps
Cation And Charge Mixing
Chemical-Vapor-Deposition
Electronic-Structure
Issue Date: 2014
Publisher: IoP Publishing Ltd
Citation: Dileep, K; Loukya, B; Silwal, P; Gupta, A; Datta, R, Probing optical band gaps at nanoscale from tetrahedral cation vacancy defects and variation of cation ordering in NiCo2O4 epitaxial thin films. Journal of Physics D-Applied Physics 2014, 47 (40), 405001 http://dx.doi.org/10.1088/0022-3727/47/40/405001
Journal of Physics D-Applied Physics
47
40
Abstract: High resolution electron energy loss spectroscopy (HREELS) is utilized to probe the optical band gaps at the nanoscale in epitaxial NiCo2O4 (NCO) thin films with different structural order (cation/charge). The structure of NCO deviates from the ideal inverse spinel (non-magnetic and insulating) for films grown at higher temperatures (>500 degrees C) towards a mixed cation structure (magnetic with metallic conductivity) at lower deposition temperatures (<450 degrees C). This significantly modifies the electronic structure as well as the nature of the band gap of the material. Nanoscale regions with unoccupied tetrahedral A site cations are additionally observed in all the samples and direct measurement from such areas reveals considerably lower band gap values as compared to the ideal inverse spinel and mixed cation configurations. Experimental values of band gaps have been found to be in good agreement with the theoretical mBJLDA exchange potential based calculated band gaps for various cation ordering and consideration of A site cation vacancy defects. The origin of rich variation in cation ordering observed in this system is discussed.
Description: Restricted Access
URI: http://hdl.handle.net/10572/2467
ISSN: 0022-3727
Appears in Collections:Research Articles (Ranjan Datta)

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