A comparative Raman study of ferroelectric PbTiO3 single crystal and thin film prepared on MgO substrate

Abstract

A Raman study of a highly oriented PbTiO3 thin film deposited on a MgO single crystal has been performed as a function of the temperature. The results have been compared with those obtained from a single crystal prepared from the same batch and those reported in the literature for polycrystalline thin films and single crystals. A shift in the transition temperature is observed from the soft mode behavior, together with more usual lower values of its frequency, which are both related to effective hydrostatic pressure due to the clamping of grains by their neighbors in the distorted tetragonal structure. The large soft mode linewidth and its integrated intensity, which do not vanish at the ferroelectric to paraelectric transition temperature, have been interpreted in terms of the coupling of this mode (and more generally of all polar phonons) with the static strain fields originating from the clamping effect and the epitaxial conditions.

Studies on ferroelectric perovskites and Bi‐layered compounds using micro‐Raman spectroscopy

“…The soft E(TO 1 ) mode in 420 nm thick film is at about 6 cm 1 below its wavenumber in the crystal. 39 The soft mode wavenumber further decreases with decreasing film thickness, as shown in Fig. 2.…”

Ferroelectric and optical properties of Ba0.8Sr0.2TiO3 thin film

“…A similar phenomenon has commonly been observed by other authors. 25 Examining the important features of the Ba 0.8 Sr 0.2 TiO 3 film spectrum in order of increasing wave number, a broadband at ϳ 241 cm Ϫ1 is observed. Next is a narrow peak at ϳ299 cm -1 .…”

Dielectric Response of Soft Modes in Ferroelectric Thin Films

“…This is attributed to hydrostatic compressive micro-stresses due to the clamping of anisotropic tetragonal grains on cooling from the cubic phase above T c (∼763 K in single crystals). In favour of this interpretation Yuzyuk et al [37] showed that the difference between the Raman soft-mode frequencies in film and crystal substantially decrease on heating to T c in correlation with the temperature dependent tetragonal deformation. It was also pointed out that the Raman strength of the soft mode remains non-zero in quite a broad interval above T c .…”