Fabrication of lead free BCZT / CFO multilayer Thin
Films by Pulsed Laser Deposition
K. Prabahar, Sai Sofiya†, Madhav Rao, Mahendran Manickam† S. V. Kamat and A Srinivas
Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad
†
Department of Materials Engineering, Thyagaraja College of Engineering, Madurai
Email: prabahardrdo@gmail.com
Abstract: A lead free piezoelectric/ferroelectric BCZT (Ba0.85Ca0.15Zr0.1Ti0.9O3) and ferrimagnetic CoFe2O4
multilayer’s were grown on Pt/Ti/SiO2/Si substrate by pulsed laser deposition using a ceramic BCZT target prepared
by conventional solid state reaction. The effect of process parameter on structure, microstructure, ferroelectric and
magnetic properties were investigated.
1.
INTRODUCTION
Magnetoelectric (ME) composite thin films of
ferroelectric and magnetic oxides have recently
stimulated increasing interests for their significant
potential applications in the next-generation novel
multifunctional devices compare to bulk ME
composites because of the easy incorporation in to the
microelectronic devices. To get large ME coefficients,
the ferroelectric layer and magnetostrictive layer
should have large piezoelectric coefficient and
magnetostrictive coefficient. So far the best
investigated piezoelectric materials are based on lead
zirconate titanate (PZT). Very recently, due to the
toxicity of lead based materials, research is focused on
lead free piezoelectric materials. BCZT (Ba0.85Ca0.15
Zr0.1Ti0.9O3) is one such lead free material which
shows large piezoelectric coefficient comparable to
PZT. Similarly CoFe2O4 has large magnetostrictive
coefficient. The ferroelectric and magnetic properties
of this material are largely controlled by deposition
parameter such as oxygen pressure and deposition
temperature. Therefore in this study we report the
ferroelectric, micro-structural and magnetic properties
of BCZT & CoFe2O4 thin films deposited on
Pt/Ti/SiO2/Si substrate with varying Oxygen pressure
and substrate temperature.
2.
Fig.1: FEG-SEM micrograph of BCZT films deposited
at Oxygen pressure of 50, 100, 200 and 400 mtorr
EXPERIMENTAL DETAILS
BCZT and CoFe2O4 targets has been prepared by
conventional solid state reaction with density greater
than 90%. Using the target BCZT & CoFe2O4 thin
films were deposited on Pt/Ti/SiO2/Si (111) substrate
with varying Oxygen power ranging from 50 mtorr to
400 mtorr and substrate temperature (575 – 7500C).
The crystal structure of the films was characterized by
Glancing Incidence XRD. Micro-structural studies
were carried out using Field Emission Gun SEM
(FEG-SEM) and domain pattern was observed by
Magnetic
Force
Microscope.
Magnetization
measurements were carried out using a SQUID –
VSM up to a maximum magnetic field of 2 Tesla.
3.
can be characterized by the appearance of (100),
(110), (200), and (111) peaks. The film deposited at
100 mtorr demonstrates a preferred crystallization in
the (111) direction, while the (100) and (110) were
less pronounced. A granular surface morphology is
observed for all the films (Fig.1). The size of the
granules is found to increase with increasing Oxygen
Pressure. The formations of triangular shaped dense
blocks were observed with superior (111) surface
texture for the films deposited at 100 mtorr. The CFO
films are crack-free and have a compact structure.
RESULTS AND DISCUSSION
X-ray diffraction patterns of BCZT and CFO films
show a well-developed perovskite and spinel
structure. The BCZT films has random orientation and
Fig.2(a) MFM & (b) M-H of CFO films deposited at
Oxygen pressure 200 mtorr.
Magnetic Force Microscopy image (Fig.2a) reveals
stripe domain structure which strongly signify inplane anisotropy. The magnetic hysteresis loop of the
CFO film (Fig.2b) shows in-plane anisotropy with
coercivity ranging from 100 to 1500 Oe depending on
the process parameters.
ACKNOWLEDGEMENTS
We would like to thank DRDO for financial
support.