Novel functional properties at ferroelectric domain walls
Department Seminar
4:00 pm
Jorgensen Hall Room: 136
Refreshments served at 3:30 in 1st floor vending area
In ferroelectric materials, domain walls separate regions with different polarisation orientation. Fundamentally, they provide an excellent model system of the rich physics of pinned elastic interfaces, whose behaviour is key for controlling domain size and stability in technological applications. In addition, domain walls can present physical properties and a local internal structure quite different from those of the parent phase. The extreme localisation of such properties at these intrinsically nanoscale features makes them potentially useful as active components in future miniaturised electronic devices.
Particularly exciting has been the discovery of domain-wall-specific electrical conduction in many ferroelectric families. Here, I will present our scanned probe microscopy observations of such conduction at 180° domain walls in otherwise insulating Pb(Zr,Ti)O3 (PZT) thin films, highlighting the key role of oxygen vacancies and surface adsorbates, whose distribution can be modulated to reversibly control domain wall transport [1].
In the same ferroelectric samples, we also observe an unusual electromechanical response, forbidden by symmetry in the parent phase but permitted at domain walls as a result of the local symmetry breaking, and the possible emergence of a localised domain-wall-specific polarization [2]. This enhanced shear response could be technologically important for ferroelectric based surface acoustic wave devices.
Most recently, using nonlinear optical microscopy, we show that indeed there exists a planar polarisation within the domain walls of both PZT and lithium tantalate (LTO), giving rise to pronounced second-harmonic signals. Local polarimetry analysis of these signals, combined with numerical modelling, reveals the presence of Néel-like and Bloch-like configurations in PZT and LTO, respectively, with moreover signatures of domain wall chirality reversal at line defects crossing the LTO crystals [3].
References:
1. Guyonnet et al., Adv. Mat. 23, 5377 (2011); Gaponenko et al., APL 106, 162902 (2015)
2. Guyonnet et al. APL 95, 132902 (2009); Guyonnet et al., JAP 108, 042002 (2010)
3. Cherifi-Hertel et al., Nat. Comm. 8, 15768 (2017)
Bio: Patrycja Paruch was born in Poland and grew up in Zimbabwe. She obtained a magna cum laude BA in Physics from Harvard University in 2000, followed by a PhD in Physics from the University of Geneva in 2004, and post-doctoral research at Cornell University.
Patrycja joined the University of Geneva in 2007. Her group (ferro.unige.ch) uses scanned force microscopy to investigate the novel functional properties of individual ferroelectric domain walls, in addition to their static and dynamic behavior as pinned elastic interfaces. Within this broader framework, the group has recently begun to also explore biological interfaces such as proliferating epithelial cell fronts. They are also developing combined ferroelectric-carbon nanotube devices for nanoelectronics and microscopy applications, and studying the effects of strain and interfacial coupling in multiferroic epitaxial superlattice structures.
Non-scientifically, she boxes, climbs rock and ice, keeps carnivorous plants and herbivorous turtles, and is somewhat asymptotically working towards a pilot license.
In ferroelectric materials, domain walls separate regions with different polarisation orientation. Fundamentally, they provide an excellent model system of the rich physics of pinned elastic interfaces, whose behaviour is key for controlling domain size and stability in technological applications. In addition, domain walls can present physical properties and a local internal structure quite different from those of the parent phase. The extreme localisation of such properties at these intrinsically nanoscale features makes them potentially useful as active components in future miniaturised electronic devices.
Particularly exciting has been the discovery of domain-wall-specific electrical conduction in many ferroelectric families. Here, I will present our scanned probe microscopy observations of such conduction at 180° domain walls in otherwise insulating Pb(Zr,Ti)O3 (PZT) thin films, highlighting the key role of oxygen vacancies and surface adsorbates, whose distribution can be modulated to reversibly control domain wall transport [1].
In the same ferroelectric samples, we also observe an unusual electromechanical response, forbidden by symmetry in the parent phase but permitted at domain walls as a result of the local symmetry breaking, and the possible emergence of a localised domain-wall-specific polarization [2]. This enhanced shear response could be technologically important for ferroelectric based surface acoustic wave devices.
Most recently, using nonlinear optical microscopy, we show that indeed there exists a planar polarisation within the domain walls of both PZT and lithium tantalate (LTO), giving rise to pronounced second-harmonic signals. Local polarimetry analysis of these signals, combined with numerical modelling, reveals the presence of Néel-like and Bloch-like configurations in PZT and LTO, respectively, with moreover signatures of domain wall chirality reversal at line defects crossing the LTO crystals [3].
References:
1. Guyonnet et al., Adv. Mat. 23, 5377 (2011); Gaponenko et al., APL 106, 162902 (2015)
2. Guyonnet et al. APL 95, 132902 (2009); Guyonnet et al., JAP 108, 042002 (2010)
3. Cherifi-Hertel et al., Nat. Comm. 8, 15768 (2017)
Bio: Patrycja Paruch was born in Poland and grew up in Zimbabwe. She obtained a magna cum laude BA in Physics from Harvard University in 2000, followed by a PhD in Physics from the University of Geneva in 2004, and post-doctoral research at Cornell University.
Patrycja joined the University of Geneva in 2007. Her group (ferro.unige.ch) uses scanned force microscopy to investigate the novel functional properties of individual ferroelectric domain walls, in addition to their static and dynamic behavior as pinned elastic interfaces. Within this broader framework, the group has recently begun to also explore biological interfaces such as proliferating epithelial cell fronts. They are also developing combined ferroelectric-carbon nanotube devices for nanoelectronics and microscopy applications, and studying the effects of strain and interfacial coupling in multiferroic epitaxial superlattice structures.
Non-scientifically, she boxes, climbs rock and ice, keeps carnivorous plants and herbivorous turtles, and is somewhat asymptotically working towards a pilot license.