Ding Lili, Ji Ye, Zhang Xiaoyue, Wu Mengjun, Zheng Yue, Wang Biao, Chen Weijin
Micro&Nano Physics and Mechanics Research Laboratory, School of Physics, Sun Yat-sen University, Guangzhou 510275, China.
School of Physics, Sun Yat-sen University, Guangzhou 510275, China.
ACS Appl Mater Interfaces. 2021 Mar 17;13(10):12331-12340. doi: 10.1021/acsami.0c19652. Epub 2021 Mar 4.
Topological quad-domain textures with interesting cross-shaped buffer domains (walls) have been recently observed in BiFeO (BFO) nanoislands, indicating a new platform for exploring topological defects and multilevel memories. Such domain textures have nevertheless only been limited in BFO nanoislands grown on LaAlO substrates with a large lattice mismatch of ∼-4.4%. Here, we report that such exotic domain textures could also form in BFO nanoislands directly grown on a conductive substrate with a much smaller lattice mismatch and the local transport characteristics of the BFO nanoislands are distinct from the previously reported ones. The angle-resolved piezoresponse force images verify that the domain textures consist of center-divergent quad-domains with upward polarizations and cross-shaped buffer domains with downward polarizations. Interestingly, textures with multiple crosses are also observed in nanoislands of larger sizes, besides the previously reported ones with a single cross. The nanoislands exhibit strong diodelike rectifying characteristics and the quad-domains show a higher average conductance than the cross-shaped buffer domains, indicating that there is a certain correlation between the local conductance of the nanoislands and the domain textures. This transport behavior is attributed to the effect of the depolarization field on the Schottky barriers at both the substrate/BFO interface and the tip/BFO junction. Our findings extend the current understanding of the exotic quad-domain textures of ferroelectric nanoislands and shed light on their potential applications for configurable electronic devices.
最近在BiFeO（BFO）纳米岛中观察到具有有趣十字形缓冲畴（壁）的拓扑四畴纹理，这为探索拓扑缺陷和多级存储器提供了一个新平台。然而，这种畴纹理仅局限于在晶格失配约为-4.4%的LaAlO衬底上生长的BFO纳米岛中。在此，我们报告称，这种奇异的畴纹理也可以在晶格失配小得多的导电衬底上直接生长的BFO纳米岛中形成，并且BFO纳米岛的局部输运特性与先前报道的不同。角分辨压电力显微镜图像证实，畴纹理由具有向上极化的中心发散四畴和具有向下极化的十字形缓冲畴组成。有趣的是，除了先前报道的具有单个十字的纳米岛外，在更大尺寸的纳米岛中还观察到具有多个十字的纹理。这些纳米岛表现出很强的二极管状整流特性，并且四畴的平均电导率高于十字形缓冲畴，这表明纳米岛的局部电导率与畴纹理之间存在一定的相关性。这种输运行为归因于去极化场对衬底/BFO界面和针尖/BFO结处肖特基势垒的影响。我们的发现扩展了目前对铁电纳米岛奇异四畴纹理的理解，并为其在可配置电子器件中的潜在应用提供了线索。
