preparation can be applied to almost any material type-hard, soft, or combinations thereof. The number of materials for which successful TEM sample preparation with FIBs has been documented certainly reaches several hundred and spans from hard matter such as metals, ceramics, and composites to soft matter including polymers, biological materials, and even frozen liquids.The main disadvantage of FIBs, however, is caused by the nature of the milling process: the ion collisions initiating sputter removal can also lead to ion implantation and cause severe damage to the remaining bulk of the material. As the FIB lamellae method spreads to more advanced TEM techniques, various procedures have been developed to reduce or repair this damage.In this article, the major specimen preparation techniques are reviewed; the consequences of FIB-induced damage are discussed, along with strategies to reduce the damage; and an overview on applications in materials science and in related instrumental fields is presented. Specimen Preparation TechniquesSince the first-generation FIBs were mainly used as semiconductor tools, early attempts to prepare TEM specimens in an FIB also focused on semiconductor materials. The initial methods were based on mechanically polishing the sample down to an approximately 50-mm lamella and then using the FIB to cut two trenches, one from each side, leaving behind a thin electron-transparent lamella supported by bulk material on two opposite sides ( Figure 1). 2 Referring to the geometry seen in Figure 1, this method is frequently called the H-bar technique. This method was subsequently refined by employing a tripod polisher for the initial thinning of the thin slab, 3 which is particularly valuable in the case of complex semiconductor devices.In parallel, techniques were developed that make it possible to directly remove an electron-transparent lamella from a bulk specimen without mechanical polishing (see Figure 2). These so-called liftout techniques were first proposed by Overwijk et al. 4 and further developed to a routinely and reliably applicable technique for a broad materials range by Giannuzzi et al. 5 Whereas the first attempts were based on an ex situ lift-out of the lamella using a micromanipulator under an optical microscope, techniques based on an in situ lift-out of the lamella are gaining increasing importance. 6 Specimens extracted by in situ lift-out can be shaped in a number of different and 400 MRS BULLETIN • VOLUME 32 • MAY 2007 • www/mrs.org/bulletin AbstractOne of the most important applications of a focused ion beam (FIB) workstation is preparing samples for transmission electron microscope (TEM) investigation. Samples must be uniformly thin to enable the analyzing beam of electrons to penetrate. The FIB enables not only the preparation of large, uniformly thick, sitespecific samples, but also the fabrication of lamellae used for TEM samples from composite samples consisting of inorganic and organic materials with very different properties. This article gives an overview of the...

Resistive switching memories based on the valence change mechanism have attracted great attention due to their potential use in future nanoelectronics. The working principle relies on ion migration in an oxide matrix and subsequent nanoscale redox processes leading to a resistance change. While switching from a low resistive to a high resistive state, different intermediate resistance levels can be programmed by changing the maximum applied voltage, making resistive switches highly interesting for multibit data storage and neuromorphic applications. To date, this phenomenon, which is known as gradual reset, has been reported in various experimental studies, but a comprehensive physical understanding of this key phenomenon is missing. Here, a combined experimental and numerical modeling approach is presented to address these issues. Time‐resolved pulse measurements are performed to study the reset kinetics in TaOx‐based nano‐crossbar structures. The results are analyzed using a 2D dynamic model of nonisothermal drift–diffusion transport in the mixed electronic–ionic conducting oxide including the effect of contact potential barriers. The model accurately describes the experimental data and provides physical insights into the processes determining the gradual reset. The gradual nature can be attributed to the temperature‐accelerated oxygen‐vacancy motion being governed by drift and diffusion processes approaching an equilibrium situation.

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