Published online by Cambridge University Press: 01 February 2011
We have measured the dielectric and optical properties of pulsed laser deposited SrBi2Ta 2O9 and Sr0.8Bi2.2Ta2O9 thin films on MgO substrate in THz frequency region by THz time-domain spectroscopy. The imaginary parts of the dielectric constant of both the samples show broad peaks in the frequency range 0.5–1.0 THz, which may be due to the soft mode in SBT in this frequency spectrum. The difference in the real part of the dielectric constant of Sr0.8Bi2.2Ta2O9 thin films is small for MHz and THz frequencies. On the other hand, the value of real part of dielectric constant of SrBi2Ta2O9 thin films in THz frequency range is much smaller than that in MHz frequency region, indicating that SrBi2Ta2O9 is not simply displacive ferroelectric material.