Electromechanical coupled modulation of dislocation nucleationand annihilation in ferroelectric oxide films

GC Li and HH Wen and Y Zhang and H Jiang and JJ Huang and WP Zhu and Y Zheng, PHYSICAL REVIEW B, 111, 224101 (2025).

DOI: 10.1103/PhysRevB.111.224101

Ferroelectric oxide films are known for superior electromechanical properties and extensive applicationsbut are prone to brittleness and fracture in preparation, transferring, and integration for device fabrications,highlighting the contradiction between high coupling of physical properties and low ability of mechanicaldeformation. Dislocations, as one general form of plasticity, can be introduced to enhance ductility of ferro-electric films and yet remain to degrade performance and stability. It is crucial and challenging to control thenucleation and annihilation of dislocations in preparations and operations for ferroelectric oxide films, resolvingthe contradiction and satisfying the needs of different stages. Here we performed molecular dynamics to studythe evolution of dislocations in PbTiO3films. The junctions of surface and domain walls triggered the nucleationof screw dislocations under compression. Combining with mechanical loading, the external electric field thatmoved the ferroelectric domain walls controlled the nucleation sites of screw dislocations. The screw dislocationsin PbTiO3films glided and escaped under electric or mechanical fields. The stress induced by compressedor tensile deformation enabled the screw dislocations surrounded by asymmetric stress distribution to glidetowards different directions. More interestingly, the damped oscillation of stress caused by the sudden changeof electric field led to the ratchet movements of screw dislocations. The design of the changing rates of electricfield could accelerate the annihilation of dislocations. These findings provide strategies for defect engineeringin ferroelectric oxide films, precisely modulate the nucleation and annihilation of dislocations, and tackle thetrade-off between the performance and deformability

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