Unusual lattice distortion in a Ba0.5Sr0.5TiO3 thin film on a LaAlO3 substrate

Abstract

Transmission electron microscopy (TEM) of a perovskite Ba0.5Sr0.5TiO3 thin film, grown on a (001) LaAlO3 substrate by pulsed-laser ablation, reveals that the film of single-crystal quality has an unusually distorted lattice with lattice parameters a and b (parallel to the interface) larger than c (perpendicular to the interface) by 1.4%. There is evidence that the as-examined Ba0.5Sr0.5TiO3 film is a variant of its high-temperature cubic phase due to its anisotropic thermal contraction during cooling. A large lattice mismatch value of 5.7% (to be compared to the normal value of 4.13%) is observed from selected area electron diffraction patterns and high-resolution TEM images of cross-sectional specimens, which suggests that the growing high-temperature film under the film growth condition may have a larger lattice constant and a different thermal expansion behavior with respect to the bulk material.

Interface-dependent rectifying TbMnO3-based heterojunctions

“…39,41 It is well know that thin films of complex oxides grown on single crystal substrates are often distorted with a lower symmetry than the bulk lattice structure. 59,60 Misfit dislocations, disordered domains and strain are the common complexities which exist at oxide interfaces and often dictate the transport properties of the junctions. Besides the straightforward effect of lattice constant mismatch, the mismatch of thermal expansion coefficients between substrate and film also plays important roles, which can potentially leads to the sensitive dependence of the interface microstructures and properties on the growth temperature.…”

Structural and optical properties of KTa0.77Nb0.23O3 nanoplates synthesized by hydrothermal method

“…However, we find that for higher niobium concentration (x = 0.23), the scattering profile is revealed to be more diffused and enlarged. It is known that in a cubic materials, the symmetry Raman tensor has only three independent components which correspond to the irreducible components A 1g (Γ 1 ), T 2g (Γ 25 ), and E g (Γ 12 ) of a second-rank tensor, and the most important contribution to the spectrum originates from the A 1g symmetry [35]. The frequency of Raman band at 166, 214, and 274 cm −1 was due to first-order scattering induced by niobium [35].…”

“…Raman scattering investigation was performed at room temperature with a Spex1403 spectrometer with a He-Ne laser (wavelength 514.5 nm) as excitation source. It is well known that the properties of materials depend on their chemical composition and microstructure [25]. Fig.…”

Microstructure and enhanced in-plane ferroelectricity of Ba0.7Sr0.3TiO3 thin films grown on MgAl2O4 (001) single-crystal substrate

“…Some interesting results have been reported. 7 [11][12][13] In this study, a 200-nm-thick Ba 0.7 Sr 0.3 TiO 3 thin film was deposited on an MgAl 2 O 4 ͑001͒ single-crystal substrate through pulsed laser deposition using a 248 nm krypton fluoride ͑KrF͒ excimer laser ͑Lambda Physik COMPex 205͒. 1 Similar enhancement of ferroelectricity has also been realized in the thin films of strontium titanate ͑SrTiO 3 ͒, solid-solution barium strontium titanate ͑Ba x Sr 1−x TiO 3 , abbreviated as BST͒, and lead strontium titanate ͑Pb x Sr 1−x TiO 3 ͒.…”

“…The surface morphology of the BST thin films was observed using an atomic force microscope ͑AFM͒ ͑Digital Instrument Nanoscope IV͒ in tapping mode. 7,16 The surface morphology of the freshly deposited BST thin film was observed under an atomic force microscope ͑Digital Instrument Nanoscope IV͒ in tapping mode ͑images not shown here͒. The sample for the dielectric and ferroelectric measurements had a configuration of coplanar interdigital capacitor.…”