Anisotropy of the infrared-active phonon modes in the mono-domain state of tetragonal SrTiO3 (110)

摘要

With infrared and terahertz ellipsometry we investigated the anisotropy ofthe infrared active phonon modes in SrTiO3 (110) single crystals in thetetragonal state below the so-called antiferrodistortive transition at T* = 105K. In particular, we show that the anisotropy of the oscillator strength of theso-called R-mode, which becomes weakly infrared active below T*, is a valuableindicator for the orientation of the structural domains. Our results revealthat a mono-domain state with the tetragonal axis (c-axis) parallel to the[001] direction can be created by applying a moderate uniaxial stress of about2.3 MPa along the [1-10] direction (with a mechanical clamp). The resulting,intrinsic splitting of the infrared-active phonon modes is reported.