Journal
JOURNAL OF ELECTRONIC MATERIALS
Volume 45, Issue 4, Pages 2059-2065Publisher
SPRINGER
DOI: 10.1007/s11664-015-4243-1
Keywords
Variable range hopping; sol-gel process; activation energy; exchange-coupling parameter
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Funding
- Department of Atomic Energy, Board of Research in Nuclear Sciences (DAE-BRNS) [34/20/02/2015/BRNS, 2014113404RP00461-BRNS]
- DST, India [SR/FST/PSII-020/2009]
- National Science Foundation (NSF)
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1410869] Funding Source: National Science Foundation
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We report the localized charge carrier transport of two-phase composite Zn1-x Ni (x) O/NiO (0 a parts per thousand currency sign x a parts per thousand currency sign 1) using the temperature dependence of ac-resistivity rho (ac)(T) across the N,el temperature T (N) (= 523 K) of nickel oxide. Our results provide strong evidence to the variable range hopping of charge carriers between the localized states through a mechanism involving spin-dependent activation energies. The temperature variation of carrier hopping energy epsilon (h)(T) and nearest-neighbor exchange-coupling parameter J (ij)(T) evaluated from the small poleron model exhibits a well-defined anomaly across T (N). For all the composite systems, the average exchange-coupling parameter (J (ij))(AVG) nearly equals to 70 meV which is slightly greater than the 60-meV exciton binding energy of pure zinc oxide. The magnitudes of epsilon (h) (similar to 0.17 eV) and J (ij) (similar to 11 meV) of pure NiO synthesized under oxygen-rich conditions are consistent with the previously reported theoretical estimation based on Green's function analysis. A systematic correlation between the oxygen stoichiometry and, epsilon (h)(T) and J (ij)(T) is discussed.
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