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New Workfl ows


Figure 8 : Initial steps. (a) Protective deposition layer over the region of interest. (b) Bulk milling completed after fi nal bulk milling clean-up.


welding pattern relative to the grid and the sample, and the system executes the grid attachment procedure ( Figure 3a ). In the fi nal steps, the user confi rms the position of the cut pattern to separate the needle from the sample, the system cuts the nanomanipulator free, and the user verifi es that the probe is free from the lamella and retracts the nanomanipulator ( Figure 3b ). Step 4: Final thinning Before starting the fi nal thinning process, the user is prompted to confi rm the eucentric and beam coincident position of the sample in the microscope by identifying the free edge of the section in the SEM and FIB, respectively. T e system can accurately place the FIB milling patterns with the recipe once the positions of the markers are identifi ed by the user (the small cross patterns in Figures 2 a and 3 a). In a fi rst thinning step, the system mills the front and backside of the lamella with a 30 kV, ~2 nA beam at a small “pre-tilt” angle to the surface. In subsequent steps, the system repeats the milling process using progressively lower currents aſt er the user identifi es the cross-patterns on top of the section. T e system automatically thins the sample to the desired thickness ( Figure 4a ), ending with a fi nal polish at 5 kV to remove surface damage and the amorphous layer ( Figure 4b ). If required, further thinning with FIB energies down to 500 V may be employed to further reduce surface damage and ensure the sample is thin enough for the required TEM analysis.


2018 January • www.microscopy-today.com


Figure 9 : Final steps. (a) Sample during thinning process. (b) Sample after fi nal low-thinning process. Note that the thinned area becomes progressively thinner and smaller toward the center of the section.


Imaging and analysis . T e AlGaN/GaN/AlN multilayer sample, prepared using the semi-automated workfl ow, was then imaged in an T ermo Scientifi c T emis probe-corrected STEM equipped with a SuperX detector consisting of four windowless silicon driſt detectors (SDDs). Figure 5 shows STEM images of the specimen taken with a HAADF detector. Figure 5a shows an overview of the sample. T e sample has a uniform thickness of about 0.4 of the mean free path in this material. Figure 5b shows AlGaN/GaN layers at atomic-level resolution. T ese images illustrate the success of the semi-automated workfl ow in FIB-based sample preparation. Figure 6 shows element maps from an EDS spectrum image collected using 200 pA beam current for 10 min. T e EDS maps show the separations of the AlGaN/GaN/AlN layers. Lastly, Figure 7 shows the spectra from two areas of the EDS maps. Raw data illustrate the spectra from the GaN and AlN regions. T ere was no indication of Ga in the AlN region, indicating that fi nal polishing with 500 V Ga + FIB can be an excellent method for preparing high-quality Ga-containing samples. Bismuth-doped lead zirconate titanate . Ferroelectric lead zirconate titanate (PZT) thin fi lms have been intensively studied in recent years as candidates for use in ultra-large- scale-integration (ULSI) dynamic random access memories (DRAM), nonvolatile random access memories (NVRAMs


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