12 research outputs found
Polar phonons in some compressively stressed epitaxial and polycrystalline SrTiO3 thin films
Several SrTiO3 (STO) thin films without electrodes processed by pulsed laser
deposition, of thicknesses down to 40 nm, were studied using infrared
transmission and reflection spectroscopy. The complex dielectric responses of
polar phonon modes, particularly ferroelectric soft mode, in the films were
determined quantitatively. The compressed epitaxial STO films on (100)
La0.18Sr0.82Al0.59-Ta0.41O3 substrates (strain 0.9%) show strongly stiffened
phonon responses, whereas the soft mode in polycrystalline film on (0001)
sapphire substrate shows a strong broadening due to grain boundaries and/or
other inhomogeneities and defects. The stiffened soft mode is responsible for a
much lower static permittivity in the plane of the compressed film than in the
bulk samples.Comment: 11 page