Journal
JOURNAL OF APPLIED PHYSICS
Volume 121, Issue 6, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.4976011
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Funding
- National Science Foundation
- Center for Dielectrics and Piezoelectrics [IIP-1361571, 1361503]
- ITO Foundation for International Education Exchange
- Ministry of Science and Technology R.O.C. [MOST 104-2622-E-006-038-CC3]
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The d.c. conduction is investigated in the two different types of internal barrier layer capacitors, namely, (Mn, Nb)-doped SrTiO3 (STO) and CaCu3Ti4O12 (CCTO). Scanning electron microscopy (SEM) and Capacitance - Voltage (C-V) analysis are performed to estimate the effective electric field at a grain boundary, E-GB. Then, the d.c. conduction mechanism is discussed based on the J (Current density)-E-GB characteristics. Three different conduction mechanisms are successively observed with the increase of E-GB in both systems. In (Mn, Nb)-doped STO, non-linear J-E-GB characteristics is temperature dependent at the intermediate E-GB and becomes relatively insensitive to the temperature at the higher E-GB. The J-E-GB at each regime is explained by the Schottky emission (SE) followed by Fowler-Nordheim (F-N) tunneling. Based on the F-N tunneling, the breakdown voltage is then scaled by the function of the depletion layer thickness and Schottky barrier height at the average grain boundary. The proposed function shows a clear linear relationship with the breakdown. On the other hand, F-N tunneling was not observed in CCTO in our measurement. Ohmic, Poole-Frenkel (P-F), and SE are successively observed in CCTO. The transition point from P-F and SE depends on EGB and temperature. A charge-based deep level transient spectroscopy study reveals that 3 types of trap states exist in CCTO. The trap one with E-t similar to 0.65 eV below the conduction band is found to be responsible for the P-F conduction. Published by AIP Publishing.
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