Market leaders in temperature controlled
microscopy, Linkam Scientific Instruments, report on the work of Dr Sharath
Sriram, a Research Fellow at RMIT University in Melbourne, Australia. He uses
Linkam specialist temperature stages with micro-Raman spectroscopy systems to
investigate temperature dependent spectral measurements.
The Functional Materials and Microsystems Research Group comprises a team of
researchers adept at thin film synthesis, microfabrication, and materials
characterisation developing platforms incorporating electronic materials for
research in fundamental physics, applied sciences, and microsystems. ARC
Australian Post-Doctoral Research Fellow, Dr. Sharath Sriram, is a key
researcher of the Group. He has expertise in the deposition and materials
characterisation of complex functional oxide thin films for electronic
applications, underpinned by skills in microelectronic fabrication techniques.
His current research interests include piezoelectrics, Raman scattering, and
electrically tunable behaviour in oxides.
Dr Sriram's interests in characterising piezoelectric thin films led him to
choose temperature controlled stages from Linkam for use in combination with a
Renishaw inVia Raman microscope. The piezoelectric effect is where an applied
pressure generates an electrical charge in certain solid materials. This
characteristic is useful for the production and detection of sound, generation
of high voltages, generation of electron frequencies, and the ultrafine
focusing of optical assemblies. This affect also forms the basis of scanning
probe microscopy techniques.
The Groups main area of work has been the investigation of the reversal and
pinning of Curie point transformation in thin film piezoelectrics. Using The
HFS91-PB4 (HFS600) Linkam stage PSZT thin films were heated to 350°C and cooled
at 10°C/min in situ with real-time collection of Raman spectra. This enabled
the researchers to determine two main Raman peaks for the film at room
temperature, ~575 and ~744cm-¹ (at which point the film had a rhombohedral
structure). Controlled heating and cooling of the thin film causes peaks and
intensity changes at the Curie point. This is indicative of a phase change
occurring at the Curie point, where the film changes from a rhombohedral
arrangement to a symmetrical cubic arrangement. This phase change coincides
with loss of piezoelectric charge and piezoelectrical structure. With
controlled cooling the cubic phase reverses back to the rhombohedral phase with
minimum hysteresis, and piezoelectrical potential.
This Curie point transformation from cubic to rhombohedral can be disrupted by
uncontrolled cooling, which results in locking in place the peak positions and
intensities indicating a permanent phase change and the material remaining
"locked" in the cubic phase. This shows fast cooling permanently
removes the piezoelectric charge within a material.
Future research will make use of the probe capability of the stage to apply an
electrical bias and study Raman spectrum changes in various piezoelectric thin
film samples.
Visit Linkam at
www.linkam.co.uk and
learn about the broad range of applications in the field of temperature
controlled microscopy.
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