Strain-Induced Phenomena in Complex Oxide Films Studied by Advanced Scanning Probe Microscopy

Yi-Chun Chen^1,2*, Yi-De Liou¹, Sheng-Zhu Ho¹, Pao-Wen Shao³, Jan-Chi Yang^1,2, Ying-Hao Chu⁴

¹Department of Physics, National Cheng Kung University, Tainan, Taiwan
²Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University, Tainan, Taiwan
³Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
⁴Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Yi-Chun Chen, email:ycchen93@mail.ncku.edu.tw

Advances in thin-film growth techniques by strain engineering have improved various physical properties in advanced functional material. For example, the epitaxial strain in multiferroic BiFeO₃ (BFO) films induced relatively large ferroelectric polarization at room temperature, which makes BFO materials appealing for applications in non-volatile devices. Moreover, the huge or asymmetric strain can induce phase transitions in epitaxial films and, in particular, create mixed-phase systems that mimic morphotropic phase boundaries. Strain-modulated homo-/hetero-interfaces in complex oxides also attract lots of interests due to their unique physical properties through couplings of spin, charge, orbital and lattice orderings between two neighboring materials. In these complex oxide systems, the versatility and the tunability via external stimuli leave many relevant mechanisms still underexplored. In this presentation, we will demonstrate studies on strain-induced phenomena in complex oxide films by lab-developed advanced scanning probe microscopy, including vector piezoresponse force microscopy, band-excitation mapping, and machine-learning based spectrum analysis. The discussed research topics will involve optical control multiferroic orderings, strain-induced super-domains, flexoelectric dipoles in centrosymmetric crystals, and anti-ferroelectric detection with zero remnant polarization states.

Keywords: complex oxides, scanning probe microscopy, surface and interface physics, strain effects