Tip Induced Surface Defect migration and Conductivity Studies in Rhombohedral epitaxial BiFeO3 Thin Films

M V, Sreenath and Ramadurai, Ranjit (2018) Tip Induced Surface Defect migration and Conductivity Studies in Rhombohedral epitaxial BiFeO3 Thin Films. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

Bismuth ferrite BiFeO3 (BFO) is the most concerned room temperature multiferroic material because of its relatively large magnetoelectric coupling. In this chapter, the electrically excited defect migration and the conductivity mechanism in BFO parent phase (rhombohedral) is demonstrated and explained. Approximately 29 nm thick BFO films are grown on LAO substrate using LSMO as the conducting bottom electrode. The rhombohedral phase is confirmed with high-resolution x-ray diffraction studies and a high strain relaxation in the film is confirmed with reciprocal space mapping. The conductivity map of the specimen is obtained with the help of a atomic force microscopy operated in the conductive mode. Electrically excited tip-induced defect migration across the specimen is observed and an enhanced conductivity in the grain boundaries are obtained which is suspected to be because of the defect accumulation at the same. The conductivity profile of the grain boundaries is studied with different applied bias voltages. Apart from local conductivity measurements, macroscopic conductivity measurements are also performed on the specimen using a probe station and a 1.16104 Ωm room temperature resistivity is obtained for the rhombohedral phase. The nono scale conductivity measurements and the macroscopic I-V curve measurements are in good conformity with each other.

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