The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, Tennessee 37831, United States.
Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, Tennessee 37831, United States.
ACS Appl Mater Interfaces. 2016 Nov 2;8(43):29588-29593. doi: 10.1021/acsami.6b10784. Epub 2016 Oct 20.
Domain formation and ferroelectric switching is fundamentally inseparable from polarization screening, which on free surfaces can be realized via band bending and ionic adsorption. In the latter case, polarization switching is intrinsically coupled to the surface electrochemical phenomena, and the electrochemical stage can control kinetics and induce long-range interactions. However, despite extensive evidence toward the critical role of surface electrochemistry, little is known about the nature of the associated processes. Here we combine SPM tip induce polarization switching and secondary ion mass spectrometry to explore the evolution of chemical state of ferroelectric during switching. Surprisingly, we find that even pristine surfaces contain ions (e.g., Cl) that are not anticipated based on chemistry of the system and processing. In the ferroelectric switching regime, we find surprising changes in surface chemistry, including redistribution of base cations. At higher voltages in the electroforming regime significant surface deformation was observed and associated with a strong ion intermixing.
畴形成和铁电开关与极化屏蔽从根本上是不可分割的，在自由表面可以通过能带弯曲和离子吸附来实现。在后一种情况下，极化切换本质上与表面电化学现象相关联，并且电化学阶段可以控制动力学并诱导远程相互作用。然而，尽管有大量证据表明表面电化学的关键作用，但对于相关过程的性质知之甚少。在这里，我们结合 SPM 针尖诱导极化切换和二次离子质谱来探索铁电切换过程中化学状态的演变。令人惊讶的是，我们发现即使是原始表面也包含了根据系统化学和处理过程不预期的离子（例如 Cl）。在铁电切换区域，我们发现表面化学性质发生了惊人的变化，包括碱基阳离子的重新分布。在电形成区域的较高电压下观察到明显的表面变形，并伴随着强烈的离子混合。
