Epitaxial ferroelectric Ba0.5Sr0.5TiO3 thin films for room-temperature tunable element applications

Abstract

Perovskite Ba0.5Sr0.5TiO3 thin films have been synthesized on (001) LaAlO3 substrates by pulsed laser ablation. Extensive x-ray diffraction, rocking curve, and pole-figure studies suggest that the films are c-axis oriented and exhibit good in-plane relationship of 〈100〉BSTO//〈100〉LAO. Rutherford backscattering spectrometry studies indicate that the epitaxial films have excellent crystalline quality with an ion beam minimum yield χmin of only 2.6%. The dielectric property measurements by the interdigital technique at 1 MHz show room-temperature values of the relative dielectric constant, εr, and loss tangent, tan δ, of 1430 and 0.007 with no bias, and 960 and 0.001 with 35 V bias, respectively. The obtained data suggest that the as-grown Ba0.5Sr0.5TiO3 films can be used for development of room-temperature tunable microwave elements.

Improvement of dielectric loss tangent of Al2O3 doped Ba0.5Sr0.5TiO3 thin films for tunable microwave devices

“…Therefore, the working temperature of the tunable microwave devices can be tuned as well. [5][6][7][8] Unfortunately, the dielectric loss ͑tan ␦͒ of the BST is normally high, being around 0.03 for xϭ0.5 in our present study. The reported values of tan ␦ for BST from different research groups are varied.…”

Influence of depolarization field on polarization states in epitaxial ferroelectric thin films with nonequally biaxial misfit strains

“…[1][2][3][4][5] An epitaxial ferroelectric thin film may have different material properties from its bulk counterpart due to the existence of a stronger depolarization field and lattice mismatch between the film and its substrate. For example, the depolarization field may suppress the ferroelectric property in ultrathin films and change the phase transition order.…”

Effects of nonequally biaxial misfit strains on the phase diagram and dielectric properties of epitaxial ferroelectric thin films

“…[1][2][3][4][5] The misfit strains between a ferroelectric thin film and its substrate are able to change the Curie temperature, the order of the paraelectric/ferroelectric phase transition, the equilibrium polarization states, and the dielectric properties of the material. 6 Certainly, a deep understanding of the relationship between the misfit strains and the material properties will provide guidelines on how to control the material properties by manipulating the misfit strains, which might be crucial for applications of ferroelectric thin films.…”