Chan Ho Leung, Fields Shelby S, Chen Yueyun, O'Neill Tristan P, Lenox Megan K, Hubbard William A, Ihlefeld Jon F, Regan Brian C
Department of Physics and Astronomy, University of California, Los Angeles, California 90095, United States.
California NanoSystems Institute, University of California, Los Angeles, California 90095, United States.
ACS Nano. 2024 Jul 17;18(31):20380-8. doi: 10.1021/acsnano.4c04526.
Better techniques for imaging ferroelectric polarization would aid the development of new ferroelectrics and the refinement of old ones. Here we show how scanning transmission electron microscope (STEM) electron beam-induced current (EBIC) imaging reveals ferroelectric polarization with obvious, simply interpretable contrast. Planar imaging of an entire ferroelectric hafnium zirconium oxide (HfZrO, HZO) capacitor shows an EBIC response that is linearly related to the polarization determined with the positive-up, negative-down (PUND) method. The contrast is easily calibrated in MV/cm. The underlying mechanism is magnification-independent, operating equally well on micrometer-sized devices and individual nanoscale domains. Coercive-field mapping reveals that individual domains are biased "positive" and "negative", as opposed to being "easy" and "hard" to switch. The remanent background -fields generating this bias can be isolated and mapped. Coupled with STEM's native capabilities for structural identification, STEM EBIC imaging provides a revolutionary tool for characterizing ferroelectric materials and devices.
更好的铁电极化成像技术将有助于新型铁电体的开发以及对现有铁电体的优化。在此，我们展示了扫描透射电子显微镜（STEM）电子束诱导电流（EBIC）成像如何以明显且易于解释的对比度揭示铁电极化。对整个铁电铪锆氧化物（HfZrO，HZO）电容器进行平面成像，结果显示EBIC响应与通过正上负下（PUND）方法测定的极化呈线性相关。这种对比度易于在兆伏/厘米单位下进行校准。其潜在机制与放大倍数无关，在微米级器件和单个纳米级畴上均能同样良好地运行。矫顽场映射显示，单个畴被偏置为“正”和“负”，而非“易”切换和“难”切换。产生这种偏置的剩余背景场可以被分离并映射。结合STEM固有的结构识别能力，STEM EBIC成像为表征铁电材料和器件提供了一种革命性的工具。
