Tuesday, February 2, 2016
Abstract-Terahertz ellipsometry study of the soft mode behavior in ultrathin SrTiO3 films
We present a combined study with time-domain terahertz and conventional far-infrared of the temperature dependent optical response of SrTiO (82 and 8.5 nm) that are by pulsed-laser deposition on (LaSr)(AlTa)O (LSAT) substrates. We demonstrate that terahertz is very sensitive to the optical response of these in particular, to the soft mode of SrTiO. We show that for the 82 nm the eigenfrequency of the soft mode is strongly reduced by annealing at 1200 °C, whereas for the 8.5 nm it is hardly affected. For the latter, after annealing the mode remains at 125 cm at 300 K and exhibits only a weak softening to about 90 cm at 10 K. This suggests that this ultrathin undergoes hardly any of the compressive strain due to the LSAT substrate.