铁电材料由于具有可被外场调控的自发极化，在信息存储与处理等领域具有重要的应用前景。借助于极化序参量与晶格、电荷自由度之间的强耦合关系，铁电性能可被多种外场调控。其中，电场和力场是两种有效的调控手段，但二者所引发的复杂效应，以及与铁电材料微观结构之间的相互作用仍有待深入理解。本论文通过原子力显微镜探针施加局部电场和力场，分别在BiFeO3薄膜中和具有极化拓扑结构的BiFeO3纳米岛中，系统研究了电场和力场对铁电极化翻转、铁电畴结构演化和阻变行为的调控，为机电微电子器件的设计提供了新思路。 在具有向上内建电场的BiFeO3薄膜中，通过改变探针所施加的应变和应变梯度，实现了力致铁电极化的可逆翻转，具有优秀的可循环性和室温稳定性。结合自由能计算和相场模拟分析了力致极化可逆翻转的机理，当探针施加大应变梯度时，挠曲电效应主导了从上至下的极化翻转，而当探针施加大应变和较小应变梯度时，压电效应和向上的内建电场主导了从下至上的极化翻转。 结合探针力场对氧空位分布的调控作用，研究了力/电多场驱动下的极化方向-氧空位分布-阻变行为之间的关联。在具有向下内建电场的BiFeO3薄膜中，基于逆Vegard效应实现了力场驱动的氧空位从薄膜上表面至下表面的迁移。再借助力/电多场调控的极化翻转，实现了受极化方向和氧空位分布控制的三种电子输运行为，包括导通方向可控铁电二极管态和绝缘态。在具有极化拓扑结构的自组装BiFeO3纳米岛中研究了力/电多场对拓扑畴结构演化和导电性的调控。通过在基片上刻蚀优先形核位点实现了有序BiFeO3纳米岛阵列的自组装生长。单个纳米岛上自发形成了由面外极化向上的中心发散四瓣畴和面外极化向下的中心汇聚过渡畴构成的中心型极化拓扑结构，核心处具有半导体型准一维导电通路。电场实现了拓扑极化结构中极化的180°铁电翻转，维持拓扑数不变；而力场的面内拖曳场可控实现了极化的71°铁弹翻转或180°铁电翻转，改变了拓扑数，驱动了中心型拓扑畴向类条纹拓扑平庸畴的转变，并且调控了拓扑畴核心处的导电性。

Ferroelectric materials, due to the switchable spontaneous polarization, have broad application potential as memories and logics. Owing to the strong coupling among polarization, charge and lattice degrees of freedom, ferroelectric properties can be modulated by multi-field. Electric field and mechanical force are effective modulating strategies, but the mechanisms of electrically and mechanically induced complex effects, and the interation between the effects and microstructures of ferroelectric thin films are not yet clear. In this thesis, by applying local electric field and mechanical force through tips of atomic force microscopy, electrical/mechanical modulation of polarization switching, ferroelectric domain evolution and resistive switching were systematically studied in BiFeO3 ferroelectric films and topological ferroelectric domains on BiFeO3 nanoislands, which enlighten the design of ferroelectric-based electro-mechanical microelectronics. In BiFeO3 films with upward built-in field, mechanically driven reversible polarization switching was realized through tip induced strain and strain gradient applied. Mechanically driven polarization switching had good recyclability and endurance at room temperature. Thermodynamic free energy calculations and phase-field simulations revealed that the up-to-down switching was driven by the flexoelectric effect when applying a large strain gradient, and the down-to-up switching was dominated by the piezoelectric effect and the upward built-in field when applying a large strain but negligible strain gradient. Combing the mechanical manipulation of the oxygen vacancy distribution, the interactions among the mechanical driven polarization switching, oxygen vacancy migration, and resistive switching were studied. In BiFeO3 films with downward built-in field, mechanical force induced converse Vegrad effect drove oxygen vacancies migration from surface to interface. With electrical and mechanical induced polarization switching, the BiFeO3 films realized tri-state resistive switching behavior, including the switchable ferroelectric diode state and the insulated state. The electrical/mechanical modulation of polar topological structures and conductivity were studied in BiFeO3 nanoisland. Self-assembly growth of highly ordered BiFeO3 nanoisland arrays were achieved by etching preferential nucleation sites on substrates. The BiFeO3 nanoislands spontaneously formed the topological domain configuration consisting the upward center-divergent quad-domain and the downward center-convergent transition domains, with quasi-one-dimensional semiconductive conduction channels at topological core. Electric field induced 180° ferroelectric switching and preserved the topological number. While the trailing field of mechanical force selectively controlled either 71° ferroelastic switching or 180° ferroelectric switching, which changed the topological number and realized the switching from topological trivial center-type domain to topologically nontrivial stripe-like domains, further manipulated the conductivity of the topological domain core.