Terahertz dielectric response of ferroelectric baxsr1-xtio3 thin films

Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba
_x
Sr
_1-x
TiO
₃
thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba
_x
Sr
_1-x
TiO
₃
thin films varies with the films compositions. Among the compositions of Ba
_x
Sr
_1-x
TiO
₃
films with different Ba/Sr ratios, Ba
_0.6
Sr
_0.4
TiO
₃
has the highest dielectric constants and the shortest dielectric relaxation time.