An improved preparation method for cross‐sectional TEM specimens of films deposited on metallic substrates

Cross‐sectional TEM analysis is one of the most important techniques to characterize microstructures of films. However, the complex process, low efficiency, and low success rate of specimen preparation limit its application. This paper analyzed the main causes of low success rate and proposed an improved method for specimen preparation of films deposited on metallic substrates. This method consisting of twin‐jet electropolishing and one‐sided rocking ion milling is high in efficiency and success rate. Microsc. Res. Tech. 79:276–279, 2016. © 2016 Wiley Periodicals, Inc.     

Imaging and analysis of 3-D structure using a dual beam FIB

The application of focused ion beam instrumentation in the generation of three-dimensional microstructural data is described. The methodologies used to acquire and manipulate this data are explained, and the technique is illustrated by a number of examples from the material sciences. The limitations of this method, and practical pointers to the generation of meaningful data, are also discussed.     

Novel techniques of preparing TEM samples for characterization of irradiation damage

Focus ion beam preparation of transmission electron microscopy (TEM) samples has become increasingly popular due to the relative ease of extraction of TEM foils from specific locations within a larger sample. However the sputtering damage induced by Ga ion bombardment in focus ion beam means that traditional electropolishing may be a preferable method. First, we describe a special electropolishing method for the preparation of irregular TEM samples from ex‐service nuclear reactor components, spring‐shaped spacers. This method has also been used to prepare samples from a nonirradiated component for a TEM in situ heavy ion irradiation study. Because the specimen size is small (0.7 × 0.7 × 3 mm), a sandwich installation is adopted to obtain high quality polishing. Second, we describe some modifications to a conventional TEM cross‐section sample preparation method that employs Ni electroplating. There are limitations to this method when preparing cross‐section samples from either (1) metals which are difficult to activate for electroplating, or (2) a heavy ion irradiated foil with a very shallow damage layer close to the surface, which may be affected by the electroplating process. As a consequence, a novel technique for preparing cross‐section samples was developed and is described.     

Combining FIB milling and conventional Argon ion milling techniques to prepare high‐quality site‐specific TEM samples for quantitative EELS analysis of oxygen in molten iron

This paper reports a procedure to combine the focused ion beam micro‐sampling method with conventional Ar‐milling to prepare high‐quality site‐specific transmission electron microscopy cross‐section samples. The advantage is to enable chemical and structural evaluations of oxygen dissolved in a molten iron sample to be made after quenching and recovery from high‐pressure experiments in a laser‐heated diamond anvil cell. The evaluations were performed by using electron energy‐loss spectroscopy and high‐resolution transmission electron microscopy. The high signal to noise ratios of electron energy‐loss spectroscopy core‐loss spectra from the transmission electron microscopy thin foil, re‐thinned down to 40 nm in thickness by conventional Argon ion milling, provided us with oxygen quantitative analyses of the quenched molten iron phase. In addition, we could obtain lattice‐fringe images using high‐resolution transmission electron microscopy. The electron energy‐loss spectroscopy analysis of oxygen in Fe_0.94O has been carried out with a relative accuracy of 2%, using an analytical procedure proposed for foils thinner than 80 nm. Oxygen K‐edge energy‐loss near‐edge structure also allows us to identify the specific phase that results from quenching and its electronic structure by the technique of fingerprinting of the spectrum with reference spectra in the Fe‐O system.     

Novel method for the plan-view TEM preparation of thin samples on brittle substrates by mechanical and ion beam thinning

A new preparation method has been developed in order to avoid the breaking of brittle samples for plan-view TEM investigation during and after mechanical and ion beam thinning. The thinning procedure is carried out on a reduced size piece of the sample (about 1.6 x 0.8 mm(2) or about 1-1.6 mm diameter) that is embedded into a 3-mm-diameter Ti disk, which fits the sample holder of the TEM. The small sample size and the supporting metal disk assure the mechanical stability and minimize the possibility of breaking during and after the preparation: The Ti disk is placed on adhesive kapton tape, a cut piece of the sample is put into the slot of the disk, pressed onto the tape and embedded with glue. The tape keeps the parts in place and in the same plane, keeps the sample surface safe from the embedding glue and can be removed easily after the glue solidifies. Subsequently, the embedded sample is thinned from the rear by well-known mechanical and ion beam techniques until electron transparency. This simple solution lowers the risk of failed sample preparation remarkably and makes it possible to reduce the thickness of the sample to about 50 microm by mechanical thinning. As a result, dimpling becomes unnecessary and low angle ion milling gives a large transparent area for TEM. Its efficiency has been proved by successful preparation of numerous thin film samples on Si, sapphire, and glass substrates. The method is compatible with the widespread cross-sectional thinning procedures, and can be easily adopted by TEM laboratories.     

Atomic force microscope (AFM) combined with the ultramicrotome: a novel device for the serial section tomography and AFM/TEM complementary structural analysis of biological and polymer samples

A new device (NTEGRA Tomo) that is based on the integration of the scanning probe microscope (SPM) (NT‐MDT NTEGRA SPM) and the Ultramicrotome (Leica UC6NT) is presented. This integration enables the direct monitoring of a block face surface immediately following each sectioning cycle of ultramicrotome sectioning procedure. Consequently, this device can be applied for a serial section tomography of the wide range of biological and polymer materials. The automation of the sectioning/scanning cycle allows one to acquire up to 10 consecutive sectioned layer images per hour. It also permits to build a 3‐D nanotomography image reconstructed from several tens of layer images within one measurement session. The thickness of the layers can be varied from 20 to 2000 nm, and can be controlled directly by its interference colour in water. Additionally, the NTEGRA Tomo with its nanometer resolution is a valid instrument narrowing and highlighting an area of special interest within volume of the sample. For embedded biological objects the ultimate resolution of SPM mostly depends on the quality of macromolecular preservation of the biomaterial during sample preparation procedure. For most polymer materials it is comparable to transmission electron microscopy (TEM). The NTEGRA Tomo can routinely collect complementary AFM and TEM images. The block face of biological or polymer sample is investigated by AFM, whereas the last ultrathin section is analyzed with TEM after a staining procedure. Using the combination of both of these ultrastructural methods for the analysis of the same particular organelle or polymer constituent leads to a breakthrough in AFM/TEM image interpretation. Finally, new complementary aspects of the object's ultrastructure can be revealed.