Temperature dependent resistivity study on zinc oxide and the role of defects |
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Authors: | Tapatee Kundu Roy D. Sanyal Debasis Bhowmick Alok Chakrabarti |
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Affiliation: | VECC, 1/AF Bidhan Nagar, Kolkata 700064, India |
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Abstract: | The temperature dependent (30–550 °C) resistivity of zinc oxide (ZnO) has been studied by the standard four probe resistivity method. The room-temperature resistivity of the sample is measured as 0.75 M Ωm. Resistivity versus temperature plot of the sample shows normal NTCR (negative temperature coefficient of resistance) behavior up to 300 °C. However, a crossover from NTCR to a PTCR (positive temperature coefficient of resistance) behavior is observed at ~300 °C. The origin of the PTCR behavior is explained with the defects present in the ZnO annealed up to 550 °C. Temperature dependent S-parameter (positron annihilation line-shape parameter) indicates the formation of oxygen vacancy like defects in this temperature region. At the PTCR region, the activation energy for the electron conduction is calculated ~2.6 eV. This value is very close to the theoretically predicted defect level energy of 2.0 eV for oxygen vacancies present in ZnO. |
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