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O: Fachverband Oberflächenphysik

O 97: Focus Session: SrTiO₃: A Versatile Material from Bulk Quantum Paraelectric to 2D Superconductor II (joint session TT/KFM/MA/O)

O 97.5: Talk

Thursday, March 21, 2024, 16:00–16:15, H 0104

IR and THz studies on (Ba_0.45Sr_0.55TiO₃)₂₄Ba_0.45Sr_0.55O and (Ba_0.45Sr_0.55TiO₃)₈Ba_0.45Sr_0.55O thin films — Veronica Goian¹, Matthew Barone², Natalie Dawley², Christelle Kadlec¹, •Darrell Schlom^2,3, and Stanislav Kamba¹ — ¹Institute of Physics ASCR, Prague, Czech Republic — ²Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA — ³Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA

(SrTiO₃)_nSrO and (n=1..6) films crystallizing in the Ruddlesdden-Popper (RP) structure are well known for low dielectric loss and large microwave permittivities which are highly tunable with electric field.^1,2 Bulk (SrTiO₃)_nSrO is paraelectric, but the tensile strained thin films deposited on (110)DyScO₃ with n≥3, become ferroelectric at low temperatures. (ATiO₃)₂₄AO and (ATiO₃)₈AO, A= Ba_0.45Sr_0.55 films deposited on (110)DyScO₃ exhibit no strain and yet become ferroelectric. Here we performed infrared and THz studies of phonon dynamics down to 10 K and compared it with above mentioned thin films and (Sr,Ba)TiO₃. The effect of soft mode and central mode on microwave dielectric properties and electric field tunability of permittivity will be discussed.

[1] C. H. Lee et al., Nature, 502 (2013) 532

[2] N. M. Dawley et al., Nat. Mater. 19 (2020) 176

Keywords: ferroelectricity; thin films; SrTiO3; Ruddlesden-Popper; soft mode