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A scanning tunneling microscopy and potentiometry study of epitaxial thin films of La0.7Ca0.3MnO3

Published online by Cambridge University Press:  11 February 2011

Mandar Paranjape ,
K. Shantha Shankar ,
A.K. Raychaudhuri ,
N.D. Mathur  and
M.G. Blamire
Mandar Paranjape
Affiliation:
Department of Physics, Indian Institute of Science, Bangalore, India 560012.
K. Shantha Shankar
Affiliation:
Department of Physics, Indian Institute of Science, Bangalore, India 560012.
A.K. Raychaudhuri
Affiliation:
Department of Physics, Indian Institute of Science, Bangalore, India 560012.
N.D. Mathur
Affiliation:
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge U.K.CB2 3QZ.
M.G. Blamire
Affiliation:
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge U.K.CB2 3QZ.
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Abstract

To investigate the role of grain boundaries and other growth related microstructure in manganite films, a scanning tunneling microscope is used to simultaneously probe surface topography and local potential distribution under current flow at nanometer level in films of epitaxial thin films of La0.7Ca0.3MnO3 deposited on single crystal SrTiO3 and NdGaO3 substrate by laser ablation. We have studied two types of films strained and strain relaxed. Thin (50nm) films (strained due to lattice mismatch between substrate and the film) show step growth (unit cell steps) and have very smooth surfaces. Relatively thicker films (strain relaxed, thickness 200nm) do not have these step growths and show rather smooth well connected grains. Charge transport in these films is not uniform on the nanometer level and is accompanied by potential jumps at the internal surfaces. In particular scattering from grain boundaries results in large variations in the local potential resulting in fields as high as 104-105V/cm located near the grain boundaries. We discuss the role of local strain and strain inhomogeneties in determining the current transport in these films and their resistance and magnetoresistivity. In this paper we attempt to correlate between bulk electronic properties with microscopic electronic conduction using scanning tunneling microscopy and scanning tunneling potentiometry.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 738: Symposium G – Spatially Resolved Characterization of Local Phenomena in Materials and Nanostructures , 2002 , G7.21
Copyright
Copyright © Materials Research Society 2003

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References

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