Department of Materials Science and Engineering , Yonsei University , Seoul 03722 , Korea.
ACS Appl Mater Interfaces. 2018 May 9;10(18):16203-16209. doi: 10.1021/acsami.8b02630. Epub 2018 Apr 24.
Colossal dielectric constant CaCuTiO has been recognized as one of the rare materials having intrinsic interfacial polarization and thus unusual dielectric characteristics, in which the electrical state of the grain boundary is critical. Here, the direct correlation between the grain boundary potential and relative permittivity is proposed for the CaCuTiO thin films doped with Zn, Ga, Mn, and Ag as characterized by Kelvin probe force microscopy. The dopants are intended to provide the examples of variable grain boundary potentials that are driven by chemical states including Cu, Ti, and oxygen vacancy. Grain boundary potential is nearly linearly proportional to the dielectric constant. This effect is attributed to the increased charge accumulation near the grain boundary, depending on the choice of the dopant. As an example, 1 mol % Ag-doped CaCuTiO thin films demonstrate the best relative permittivity as associated with a higher grain boundary potential of 120.3 mV compared with 82.6 mV for the reference film. The chemical states across grain boundaries were further verified by using spherical aberration-corrected scanning transmission electron microscopy with the simultaneous electron energy loss spectroscopy.
具有本征界面极化的巨介电常数 CaCuTiO 已被认为是具有独特介电特性的稀有材料之一，其中晶界的电状态至关重要。在这里，通过 Kelvin 探针力显微镜研究了掺杂 Zn、Ga、Mn 和 Ag 的 CaCuTiO 薄膜中晶界势与相对介电常数之间的直接关系。掺杂剂旨在提供由包括 Cu、Ti 和氧空位在内的化学状态驱动的可变晶界势的例子。晶界势与介电常数几乎呈线性关系。这种效应归因于在晶界附近积累的电荷增加，这取决于掺杂剂的选择。例如，与基准薄膜的 82.6 mV 相比，1 mol% Ag 掺杂 CaCuTiO 薄膜表现出更高的晶界势 120.3 mV，从而表现出最佳的相对介电常数。还通过使用具有同时电子能量损失光谱的球差校正扫描透射电子显微镜进一步验证了晶界处的化学状态。
