TY  - JOUR
AU  - Skoromets, V.
AU  - Kadlec, C.
AU  - Drahokoupil, J.
AU  - Schubert, Jürgen
AU  - Hlinka, J.
AU  - Kužel, P.
TI  - Systematic study of terahertz response of SrTiO$_3$ based heterostructures: Influence of strain, temperature, and electric field
JO  - Physical review / B
VL  - 89
IS  - 21
SN  - 1098-0121
CY  - College Park, Md.
PB  - APS
M1  - FZJ-2014-03653
SP  - 214116
PY  - 2014
AB  - Epitaxial heterostructures consisting of a variable number of SrTiO3/DyScO3 bilayers deposited onDyScO3 substrates were investigated using time-domain terahertz spectroscopy down to helium temperatures.Interdigitated electrodes deposited on top of the structures allowed probing of the terahertz response upon anapplied electric field. The phase transition into a ferroelectric state is observed in SrTiO3 films in all samplesclose to room temperature (between 250 and 310 K) due to in-plane epitaxial strain induced by the substrateand intercalated layers of DyScO3. Evolution of the dielectric spectra with temperature and external electricfield is described by a general model which involves a damped harmonic oscillator (soft mode) coupled to aDebye relaxation (central mode). Both modes are connected with the soft mode eigenvector, as recently shownby molecular dynamics simulations, and they reflect a strong anharmonicity of the soft-mode potential. At hightemperatures the soft-mode frequency variation drives all the changes observed in the spectra with temperatureand applied field. At low temperatures, deep in the ferroelectric phase, the soft mode significantly hardens andloses its importance for the terahertz dynamics; the central mode becomes stronger and it almost completelydetermines the shape of the measured spectra. The observed variation of phase transition temperature and of thedielectric response among the structures is ascribed to a partial epitaxial strain relaxation confirmed also by x-raydiffraction.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000339048100001
DO  - DOI:10.1103/PhysRevB.89.214116
UR  - https://juser.fz-juelich.de/record/154296
ER  -