研究目的
To demonstrate a mechanical approach to induce isolated or interacting in-plane dipole vortices in ferroelectric films by pressing an AFM-tip, and to explore the interaction between two tip-induced vortices.
研究成果
The study demonstrates a mechanical approach to induce isolated or interacting in-plane dipole vortices in ferroelectric films by pressing an AFM-tip. The formation of such dipole vortices is caused by a conjoint effect of the tip-force-induced depolarization effect and in-plane strain. The interaction between two tip-induced vortices shows that their chirality is either identical or opposite, depending on the distance between the tips. A maximum data storage density of isolated in-plane vortices in ferroelectric thin film is estimated to be ~1 Tb in?2.
研究不足
A shortcoming of the current strategy of mechanical writing in-plane dipole vortices is that the dipole vortices would not maintain stable once the tip-force is removed.
1：Experimental Design and Method Selection:
A 3D phase field model is employed to simulate the effect of mechanical tip-force on ferroelectric films. The model includes the spontaneous polarization field as the order parameter and considers various energy densities such as bulk Landau energy, gradient energy, electrostatic energy, elastic energy, and surface energy. Flexoelectric coupling energy density is also included due to the large strain gradient induced by tip-force.
2：Sample Selection and Data Sources:
The study focuses on BaTiO3 (BTO) thin films epitaxially grown on a deformable cubic substrate with a compressive in-plane misfit strain.
3：List of Experimental Equipment and Materials:
An atomic force microscopy (AFM) tip made of Pt with a radius of 50 nm is used to apply mechanical force.
4：Experimental Procedures and Operational Workflow:
The films are initialized into a single domain state with an upward polarization; then the tip-force is exerted on the films to drive them to reach new equilibrium states; finally, with the tip-force loaded off, the films are relaxed to reach final steady states.
5：Data Analysis Methods:
The temporal evolution of polarization field is described by time-dependent Ginzburg-Landau (TDGL) equations. The electric field and strain field are updated according to the temporary dipole configuration. The electric field is obtained by solving the electrostatic equilibrium equation under ideal short-circuit boundary condition, and the strain field is obtained by solving the mechanical equilibrium equation under the stress boundary conditions exerted by the tip-force and the substrate.
独家科研数据包，助您复现前沿成果，加速创新突破
获取完整内容
