SPICE Workshop on Ferrons and Magnons: friends or foes? July 7th - 9th, 2026
Ilaria Zardo
Functional oxides attract significant attention due to their wide range of properties including superconductivity, ferroelectricity, ferromagnetism, and multiferroicity. This plethora of properties arises from the strong interactions between charge, orbital, spin, and structural properties, leading to a wide range of functionalities. Among functional oxides, perovskites stand out as one of the most versatile, thanks to their integrability as thin-films into silicon-based electronics. They are suitable for applications ranging from memory transistors to optical circuits, sensors, and transducers [1]. In addition to the intrinsic properties of the bulk crystals, the possibility of nanostructuring them in a thin-film fashion opens a further degree of freedom to control their properties [2]. However, the lattice dynamics that govern their thermal and acoustic behavior after being released from substrate clamping, remain largely unexplored.
In this work, lattice dynamics and thermal properties of suspended SrTiO3 (STO) films, with thickness between 30 and 200 nm are studied. We directly probe the confined acoustic phonon spectrum of free standing (STO) membranes across a range of thicknesses using two independent, non-destructive optical techniques: Brillouin light scattering (BLS) and transient reflectivity (TR). We observe quantized confined longitudinal acoustic (LA) modes whose frequencies scale inversely with thickness, establishing the membrane geometry as a direct, designable handle on the phonon dispersion. The timeresolved measurements further probe the thickness-dependent thermal relaxation, demonstrating that membrane geometry simultaneously controls the acoustic and thermal response. Furthermore, a temperature dependent study of the in-plane thermal conductivity was conducted using a combination of the thermal bridge method [4] and the three probe technique [5], which uses a scanning laser as a heat source to correct for contact resistance. Combined with the transferability of these membranes onto arbitrary substrates, our results establish freestanding oxides as a geometrically programmable phononic and thermal platform and provide a contactless probe for measuring phonon engineering across the complex-oxide membrane family.
[1] L. Han, Adv. Funct. Mater. 2024, 34, 2309543.
[2] F. M. Chiabrera, ANNALEN DER PHYSIK, 2022, 534, 2200084.
[3] Greta Segantini, Nano Letters, 2024, 24 (45), 14191-14197.
[4] Yashpreet Kaur, ACS Applied Materials & Interfaces 2025, 17 (1), 1883-1891.
[5] Dan Liu, Nano Letters, 2014, 14 (2), 806-812.