PLD Grown Epitaxial Thin Film from Polycrystalline
Dual-phase Bulk Targets
Anjana Dogra, Pramod Kumar, Aswin.V, Pooja Singh and R. C. Budhani
Quantum Phenomena and Applications Division, CSIR-National Physical Laboratory,
Dr. K.S. Krishnan Marg, New Delhi-110012, INDIA
*
Corresponding author’s e-mail:anjanad@nplindia.org, Tel.: +91-11-45721097; Fax: +91-11-45609301
Abstract
Coexistence of dual phases in LaCo1-xAlxO3 and LaCr1xAlxO3 bulk samples, however PLD grown thin film of the
same material comes out to be single crystalline epitaxial
film. Though, the bulk samples of the same represent
insulating nature, thin film of doped systems represent the
metallic characteristic because of 2DEG at interface.
Keywords: Pulsed Laser Deposition, Reflection High Energy
Electron Diffraction, Mott Insulator, 2DEG
Introduction
Over the years several theoretical and experimental
studies have been devoted to perovskites based on
transition metal oxides. Kind and level of doping at the
cation site not only decides the ordering of charge, spin
and orbital but also impart various multifunctional
properties that arouse from strong electron correlation.
LaCoO3 and LaCrO3 are two such important perovskite
families where on one hand one is consisting of a
ferromagnetic cation Co and the other consist of Cr, an
antiferromagnetic entity. Both LaCrO3 and LaCoO3 are
Mott insulators. Recently one of the band insulator
perovskite that attracted researchers is LaAlO3 system
since it displays the existence of 2 dimensional electron
gas (2DEG) at the interface with the SrTiO3 substrate.
Thus we come up with two different systems where we
dope Al at Co and Cr site in LaCoO3 and LaCrO3
respectively.
Results
In the present work we not only present the structural
and magnetization results of the pure and the Al doped
bulk samples. But we also exhibit the results for the
Pulsed laser deposited thin films from these bulk
samples. Here we show that the bulk doped samples
exhibit the coexistence of two phases in the Rietveld
refined x-ray diffraction pattern, however the thin films
grown using these target are single crystalline epitaxial
films. Pristine LaCoO3 and LaCrO3 in bulk and thin film
are insulators. However thin film of Al doped samples
exhibit the metallic characteristic in the resistivity
measurements. This metallic nature is correlated to the
presence of 2DEG at the interface with TiO2 terminated
STO substrate.
Fig. 1: (left) Rietveld refined XRD pattern for bulk
LaAl0.5Co0.5O3. (right) Omega scan, Rocking curve for
50nm LaAl0.5Co0.5O3/SrTiO3.
Experimental Details
Acknowledgment
Bulk sample of LaCo1-xAlxO3 and LaCr1-xAlxO3 were
prepared by solid state reaction method. Films with the
thickness of 8nm and 50 nm for all the compositions
were fabricated on the TiO2 terminated SrTiO3 (001)
single crystal substrates using Pulsed laser deposition
(PLD)
technique.
Thin
films
of all
the
compositions were deposited at 800 0C at the oxygen
partial pressure of 1x10-4 mbar. Deposition was
performed using KrF laser ( = 248 nm) with the
repetition rate of 1 Hz and energy density in the range
of 0.56-0.65 J.cm-2. The film growth mode and
thickness were monitored using in-situ RHEED during
deposition. Structural characterizations of all the
deposited films were performed using PANalytical
X’Pert MRD X-ray diffractometer with Cu K1
radiation with the wavelength of 1.54 A°. Transport
measurements were done in Vander Pauw geometry
using closed cycle refrigerator.
Anjana Dogra acknowledges IFCPAR for the funding
through project no. 4704-1. Dr. K. K. Maurya is
acknowledged for the XRD measurements.
References
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electron gas at the LaAlO3/SrTiO3 heterointerface”,
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