Ferroelectric phase transitions in three-component short-period superlattices studied by ultraviolet Raman spectroscopy

Abstract

Vibrational spectra of three-component BaTiO 3 /SrTiO 3 /CaTiO 3 short-period superlattices grown by pulsed laser deposition with atomic-layer control have been investigated by ultraviolet Raman spectroscopy. Monitoring the intensity of the first-order phonon peaks in Raman spectra as a function of temperature allowed determination of the ferroelectric phase transition temperature, T c . Raman spectra indicate that all superlattices remain in the tetragonal ferroelectric phase with out-of-plane polarization in the entire temperature range below T c . The dependence of T c on the relative thicknesses of ferroelectric (BaTiO 3 ) to non-ferroelectric materials (SrTiO 3 and CaTiO 3 ) has been studied. The highest T c was found in superlattices having the largest relative amount of BaTiO 3 , provided that the superlattice maintains its coherency with the substrate. Strain relaxation leads to a significant decrease in the ferroelectric phase transition temperature.

Lattice-constant prediction and effect of vacancies in aliovalently doped perovskites

“…In addition, 13 compositions in the system Ca 1À3x Ln 2x TiO 3 (Ln = La, Nd, Y), two compositions in the system Pb 1À3x La 2x TiO 3 , four compositions in the system Ba 1À3x La 2x TiO 3 , six compositions in the system Pb 1À3x La 2x (Zr 0. 6 PLZT compositions (0 6 x 6 0.03) were processed via attrition milling according to the method previously described by Tolman et al [37].…”

“…The design of materials with these properties is aided by an understanding of the relationship between chemical composition and crystal structure. In particular, the prediction of the cubic or pseudocubic lattice constant of perovskite materials is of importance partially for their use as substrates or buffer layers for compound semiconductor epitaxy [1,2] or as strain layers in ceramic superlattice structures [3][4][5][6][7]. An example of the latter is BaTiO 3 /SrTiO 3 superlattices in which the tensile and compressive properties of each alternating layer of ferroelectric BaTiO 3 induces ferroelectric properties in the SrTiO 3 , and the SrTiO 3 layers compensate for the relaxation of the strain in BaTiO 3 with film thickness, making it possible to grow thicker ferroelectric films and enabling the tuning of properties by varying the thickness of each layer.…”

Influence of interfacial coherency on ferroelectric switching of superlattice BaTiO3/SrTiO3

“…[5][6][7][8][9][10][11][12][13][14][15][16] Due to the presence of misfit dislocations, however, the ferroelectric behavior of the superlattices is strongly influenced by the mechanical boundary conditions between the BT/ST superlattice film and its underlying substrate. In particular, the relaxation between the thin film/substrate interface can greatly affect the ferroelectric domain structure, 17 phase transition temperature, 18,19 dielectric properties, 20 remanent polarization, 21 and the hysteresis loop of polarization vs. externally applied electric field (P-E loop). [22][23][24] Thus, it is essential to investigate the ferroelectric properties together with the domain microstructures to understand the influence of strain relaxation within BT/ST superlattices.…”

Strain-coupled ferroelectric polarization in BaTiO3–CaTiO3 superlattices

“…9,10 Recently, by including PE CaTiO 3 (CTO) layers, three-component SLs have been designed and raised an intriguing issue of artificially broken compositional inversion symmetry, 11,12 resulting enhanced ferroelectric properties. 7,13 Along with these experimental developments, recent progress in computational methods [14][15][16] have provided us with opportunities to systematically investigate these FE oxide SLs as well. [17][18][19][20] Especially, Nakhmanson et al performed ab initio calculations combined with a genetic algorithm technique to optimize the arrangement of individual BTO, STO, and CTO layers in a SL form, and found that (BTO)n/(CTO)n SLs, where n is the number of unitcells (u.c.)…”