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_xSr_1-xTiO₃ 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_xSr_1-xTiO₃ thin films varies with the films compositions. Among the compositions of Ba_xSr_1-xTiO₃ films with different Ba/Sr ratios, Ba_0.6Sr_0.4TiO₃ has the highest dielectric constants and the shortest dielectric relaxation time.