arXiv subjects

Johanna van Gent González

Publications and source records attributed to Johanna van Gent González.

3 recordsLinked to original sources

arXiv2026

Super-tetragonal ferroelectric barium titanate through anionic overstoichiometry

Ferroelectric oxides, characterized by an electrical polarization that is switchable with an electric field, are an appealing class of materials for energy-efficient computing, electronics, and photonics. In thin films, the properties of ferroelectrics are commonly tuned using substrate-imposed epitaxial strain, an approach limited to biaxial strain states and a finite number of available substrates. Here, we demonstrate that is is possible to move beyond conventional epitaxial growth by using pulsed laser deposition under highly non-equilibrium conditions. Specifically, we show that this unconventional processing route allows us to stabilize a super-tetragonal phase of ferroelectric $\text{BaTiO}_3$. The key to this stabilization lies in the insertion of surplus oxygen atoms into the unit cell, resulting in peroxide bond formation that give rise to an aspect ratio of as high as 1.08. Notably, this super-tetragonal phase exhibits an enhanced ferroelectric polarization, reduced coercivity, lower leakage currents, and increased cycling endurance compared to conventional bulk-like $\text{BaTiO}_3$ films. These results, thus, showcase the potential of non-equilibrium growth for defect engineering to obtain emergent phases in complex oxides and tune their physical properties in thin films expanding the scope of traditional epitaxy.

cond-mat.mtrl-sci↗

arXiv2026

Domain-wall-to-domain interconversion in a polar conducting oxide

Domain walls in ferroic crystals are topological defects with a symmetry distinct from the domain interior, allowing them to display functionalities that are otherwise forbidden in the host material. Despite their unique properties, domain walls are strictly confined to two-dimensional interfaces, which hinders unveiling their true nature and limits their applicability. Here, we demonstrate reversible dimensionality control by expanding nanoscale domain walls into three-dimensional functional regions in polar epitaxial tungsten trioxide ($\text{WO}_3$). This domain-wall-to-domain interconversion is enabled by the conducting, non-polar domain walls adopting the parent-phase structure. An alternating electric field applied through a scanning probe tip induces localized heating, which expands this domain-wall phase into the adjacent polar domains. This approach enables reversible spatial control to switch between mutually exclusive properties of domains (polarity) and domain walls (conductivity), offering a new paradigm for reconfigurable oxide electronics.

cond-mat.mtrl-sci↗

arXiv2025

Polarity and anti-distortive polarons in WO3 through epitaxial shear strain

Bestowing CMOS-compatible binary oxides with additional functionalities is a powerful strategy toward the realization of oxide electronics. Ideal candidates are thin films which display a strong sensitivity to strain, chemical doping or nanoscale confinement. Among these, crystalline tungsten trioxide WO3 exhibits exceptional structural flexibility, enabling a wide range of functionalities. Here, we reveal the emergence of a previously unreported polar phase in epitaxial WO3 thin films. We accomplish this by imposing epitaxial shear strain, which stabilizes a low-symmetry triclinic structure that persists up to large film thicknesses and elevated temperatures. At the atomic scale, a change in the oxygen octahedral tilt pattern facilitates this symmetry lowering into a polar phase, which manifests as a periodic in-plane polarized stripe domain configuration with needle-like bifurcations at the microscale. The stripe domain walls further exhibit a strongly enhanced electrical conductivity in conjunction with a pronounced reduction of a distortive structural mode, providing the first experimental evidence for the formation of anti-distortive polarons recently predicted in WO3.

cond-mat.mtrl-sci↗