New Workfl ows Broaden Access to S/TEM Analysis and Increase Productivity
Brandon Van Leer , 1 * Remco Geurts , 2 Raphaela Scharfschwerdt , 2 Huikai Cheng , 1 Letian Li , 2
and Robert Imlau 2 1 T ermo Fisher Scientifi c , 5350 NE Dawson Creek Drive , Hillsboro , OR 97124 2 T ermo Fisher Scientifi c , Achtseweg Noord 5 , 5651 GG , Eindhoven , Netherlands
*
brandon.van.leer@thermofi
sher.com
Abstract: The DualBeam, which combines focused ion beam and scanning electron microscope (FIB-SEM), is regularly used for sample preparation in transmission electron microscopy (TEM). A DualBeam enables the user to thin specifi c regions of a bulk material to electron transparency. While this process is often performed manually, we describe an interactive guided TEM sample preparation process. By this method, the preparation process time is shortened for expert users, compared to manual processes, and enables novice users to obtain high-quality results routinely. The method can be used on almost any material to prepare thin lamellas for most common TEM applications.
Keywords: interactive workfl ow, focused ion beam (FIB) milling, scanning electron microscopy (SEM), site-specifi c thin specimen preparation, transmission electron microscopy (TEM)
Introduction
One of the most time-consuming tasks in materials characterization labs is the preparation of high-quality samples for high-resolution S/TEM (transmission and/or scanning transmission electron microscopes, collectively) analysis. T e samples must be thin—as thin as a few tens of nanometers— and thinner is almost always better for high-resolution images. Creating such samples without damaging the structures of interest is challenging, to say the least. Traditional methods can take several hours to many days to complete and, even in the most expert hands, may still deliver samples of insuffi cient quality.
Focused ion beam (FIB) and DualBeam FIB/SEM (scanning electron microscope) technologies have long been the methods of choice to create site-specific samples that must contain a specific structure from a known location within the bulk sample [ 1 ]. Recent advances in microscope technology, especially in the area of automation, have dramatically increased the speed, ease, and reliability of the preparation process, ensuring fast, high-quality results [ 2 , 3 ]. This is even the case for less experienced operators, making the technique a viable alternative to conventional methods even when site specificity is not required. In this article, we will review the requirements for high-quality samples in S/TEM analysis, outline the benefits of using FIB/SEM technology for S/TEM sample preparation, present a novel approach to S/TEM sample preparation based on a guided workfl ow, and demonstrate the workfl ow as part of a use case.
Materials and Methods T in specimen requirements . High-resolution scanning/ transmission electron microscopy (HR-S/TEM) is an excellent method for studying the structure of materials at the atomic level [ 4 ]. Modern TEMs can correct for the spherical aberra- tions inherent in the magnetic lenses used to focus electrons,
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provide direct visualization of the atomic order of crystals, and determine the position of individual atoms to within a few tens of picometers. Obtaining the best results in HR-S/TEM requires near-perfect samples [ 5 ]. In addition to acquiring high-quality data from a single sample, the scientifi c method requires that the results also be reproducible, meaning that other samples extracted from a bulk material by the same operator or another operator should deliver the same results with regards to structure, morphology, and elemental composition. In order to achieve these high-quality, reproducible results, the samples must exhibit certain characteristics:
Figure 1 : Protection of the region of interest and chunk milling. (a) Deposition layer that protects the chunk sample during the milling process. (b) Completed bulk milling step with bulk milling clean-up.
doi: 10.1017/S1551929517001195
www.microscopy-today.com • 2018 January
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