Smith Kevin A, Ramkumar Sriram P, Du Kai, Xu Xianghan, Cheong Sang-Wook, Gilbert Corder Stephanie N, Bechtel Hans A, Nowadnick Elizabeth A, Musfeldt Janice L
Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States.
Department of Materials Science and Engineering, University of California, Merced, California 95343 United States.
ACS Appl Mater Interfaces. 2023 Feb 8;15(5):7562-7571. doi: 10.1021/acsami.2c19600. Epub 2023 Jan 30.
We employ synchrotron-based near-field infrared spectroscopy to image the phononic properties of ferroelectric domain walls in hexagonal () LuScFeO, and we compare our findings with a detailed symmetry analysis, lattice dynamics calculations, and prior models of domain-wall structure. Rather than metallic and atomically thin as observed in the rare-earth manganites, ferroelectric walls in -LuScFeO are broad and semiconducting, a finding that we attribute to the presence of an -site substitution-induced intermediate phase that reduces strain and renders the interior of the domain wall nonpolar. Mixed Lu/Sc occupation on the site also provides compositional heterogeneity over micron-sized length scales, and we leverage the fact that Lu and Sc cluster in different ratios to demonstrate that the spectral characteristics at the wall are robust even in different compositional regimes. This work opens the door to broadband imaging of physical and chemical heterogeneity in ferroics and represents an important step toward revealing the rich properties of these flexible defect states.
我们采用基于同步加速器的近场红外光谱对六方（）LuScFeO中铁电畴壁的声子特性进行成像，并将我们的研究结果与详细的对称性分析、晶格动力学计算以及先前的畴壁结构模型进行比较。与在稀土锰酸盐中观察到的金属性且原子级薄的情况不同，-LuScFeO中的铁电壁较宽且为半导体性质，我们将这一发现归因于存在一个由位点取代诱导的中间相，该中间相减少了应变并使畴壁内部呈非极性。位点上的Lu/Sc混合占据还在微米级长度尺度上提供了成分异质性，并且我们利用Lu和Sc以不同比例聚集这一事实来证明，即使在不同的成分体系中，畴壁处的光谱特征也是稳健的。这项工作为铁电体中物理和化学异质性的宽带成像打开了大门，代表了朝着揭示这些灵活缺陷态的丰富特性迈出的重要一步。
