Imaging Ferroelectrics: Reinterpreting Charge Gradient Microscopy as Potential Gradient Microscopy
Imaging Ferroelectrics: Reinterpreting Charge Gradient Microscopy as Potential Gradient Microscopy
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DOI：
10.1002/aelm.202101384
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发表时间：
2022-03
影响因子：
6.2
通讯作者：
J. R. Maguire;Hamza Waseem;R. G. McQuaid;Amit Kumar;J. Gregg;C. Cochard
中科院分区：
文献类型：
--
作者：
J. R. Maguire;Hamza Waseem;R. G. McQuaid;Amit Kumar;J. Gregg;C. Cochard
电荷梯度显微镜 (CGM) 是一种扫描探针成像模式，特别适合铁电体的表征。该技术的实施很简单；它涉及监测当被动传导原子力显微镜尖端在样本表面上扫描时自发产生的电流。然而，关于对比度的基本起源的细节以及图像在相关铁电微结构方面的含义尚未完全了解。在这里，通过比较从同一组铁电域（铌酸锂和钛酸钡）获得的 CGM 和开尔文探针力显微镜的信息，表明 CGM 合理地反映了测量的表面电势的空间导数。这在概念上不同于测量表面束缚电荷密度或任何相关屏蔽电荷中的局部梯度：毕竟，即使极化完全在平面内（其中束缚电荷密度一致为零，但表面电势梯度仍然是完全预期的），也可以看到清晰的 CGM 信号。因此，建议铁电体中的 CGM 可能更准确地称为电位梯度显微镜。
Charge gradient microscopy (CGM) is a scanning probe imaging mode, particularly well‐suited for the characterization of ferroelectrics. The implementation of the technique is straightforward; it involves monitoring currents that spontaneously develop between a passive conducting atomic force microscopy tip and Earth, as the tip is scanned across the specimen surface. However, details on the fundamental origin of contrast and what images mean, in terms of associated ferroelectric microstructures, are not yet fully understood. Here, by comparing information from CGM and Kelvin probe force microscopy, obtained from the same sets of ferroelectric domains (in both lithium niobate and barium titanate), it is shown that CGM reasonably reflects the spatial derivative of the measured surface potential. This is conceptually different from measuring local gradients in the surface bound‐charge density or in any associated screening charges: after all, clear CGM signals are seen, even when polarization is entirely in‐plane (where the bound charge density is uniformly zero, but gradients in surface potential are still fully expected). It is therefore suggested that CGM in ferroelectrics may be more accurately called potential gradient microscopy.