Time of flight-secondary ion mass spectrometry (ToF-SIMS) has been used to obtain the composition in depth of a few nanometers thick layer of lanthanum aluminate prepared by molecular beam epitaxy. The electrical properties of the films were probed by piezoresponse force microscopy (PFM) and Kelvin Force Microscopy (KFM). From PFM images, the sample under study behaves exactly as if it was ferroelectric although it is amorphous: this is a major artefact of this technique. This effect has often been related to the migration of oxygen vacancies within the sample, which modifies the molar volume under the AFM tip. ToF-SIMS results show that this effect may rather be due to the migration of lanthanum instead of oxygen vacancies. The authors also show that scanning with the tip of an atomic force microscope induces some chemical modifications at the surface. This combined methodology (ToF-SIMS, PFM, and KFM) allows one to better understand the contrast mechanisms at play during scanning probe experiments, especially when high electric fields and ionic migrations are involved.

中文翻译：

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通过飞行时间-二次离子质谱和压电响应力显微镜联合方法研究铝酸镧极化过程中的离子迁移

飞行时间-二次离子质谱 (ToF-SIMS) 已被用于获得分子束外延制备的几纳米厚铝酸镧层的成分。通过压电响应力显微镜（PFM）和开尔文力显微镜（KFM）探测薄膜的电性能。从 PFM 图像来看，所研究的样品虽然是非晶态的，但表现得就像是铁电体：这是该技术的主要产物。这种效应通常与样品内氧空位的迁移有关，这会改变 AFM 尖端下的摩尔体积。ToF-SIMS 结果表明，这种效应可能是由于镧的迁移而不是氧空位的迁移。作者还表明，用原子力显微镜的尖端扫描会在表面引起一些化学修饰。这种组合方法（ToF-SIMS、PFM 和 KFM）可以让人们更好地了解扫描探针实验期间的对比机制，尤其是在涉及高电场和离子迁移时。