TEM Sample Preparation and FIB-Induced Damage

Abstract

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...

Magnetic characteristics of a high-layer-number NiFe/FeMn multilayer

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“…11 Ion collisions lead to the removal of the milled material through a process that is not strongly dependent on oxide composition. 11 Ion-induced damage is a significant concern, however, in the use of FIB to create oxide nanostructures. The generation of defects during FIB is described using a collision cascade model, in which ions participate in a series of independent two-body collisions.…”

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