April_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 0 2 8 a wide of range of materials, including various chloride complexes, extrater- restrial particle specimens, radioactive materials, and more. Figure 3 shows images of a posi- tive electrode containing LiCoO 2 parti- cles in a battery that was charged and discharged five times with and with- out air exposure. The images highlight growth of an oxide layer and structural alterations after air exposure. NANOSTRUCTURED MATERIALS Another development in SEM tech- nology is the ability to acquire low-volt- age images that can help in imaging and analysis of thin surface layers (e.g., atomic layer grapheneandboronnitride sheets), nanoporous materials (e.g., zeo- lites and polymer membranes), and ex- tremely electron beam-sensitive mate- rials [2] . Very low voltage (down to 10 V) is achievable through a combination of advanced electron optics and detec- tor design, gentle beam capability, and NeoEngine capability. NeoEngine is an artificial intel- ligence-driven capability that tracks electron beam trajectories and align- ment parameters and adjusts them as the user changes imaging and analysis parameters to assure the best imaging conditions at all times. The NeoEngine operates in the background; the user experiences seamless operation of the instrument with minimal effort to acquire images even at extreme- ly low voltages on difficult specimens. Figure 4 shows a few examples of low- voltage imaging. The use of SEM also facilitates both imaging and EDS analysis of graphene layers with respect to the substrate, thus providing a more direct analysis of graphene in its application-based environment. This is in contrast to TEM, where only individual suspend- ed sheets of graphene can be imaged. Figure 5 shows an example of EDS maps of graphene layers on Ni substrate, ob- tained at 1 kV and 5 kV. By performing EDS analysis at low accelerating voltage, the beam-speci- men interaction volume is significant- ly reduced so that discrete maps of graphene and Ni components can be resolved. In order to minimize any sig- nificant buildup of carbon contamina- tion on the sample surface that could obscure characterization, the map- ping time was less than 5 min. The high beam current setting, combined with the large-area detector (100 mm 2 ) used for this analysis, ensured adequate data collection for compositional interpreta- tion, even with a short acquisition time at low kV. 3D ANALYSIS OF SURFACES The long depth of field associat- ed with SEM imaging has traditionally been appealing to researchers because of the inherent ability to provide a more three-dimensional representation of the specimen surface, as compared to optical microscopy. However, a con- certed effort has been made in recent years to take this capability even fur- ther, with various software and hard- ware solutions utilized to provide not only qualitative but also quantitative representation of the 3D nature of spec- imen surfaces. Solutions range from a simple com- bination of two or more stereo pair im- ages (Fig. 6a) to the actual redesign of detectors to acquire multiple images simultaneously. Those images can be combined to create a live 3D represen- tation of the specimen surface that can be manipulated, tilted, and rotated by the user (Fig. 6b). EXPANDING SEM AVENUES The use of innovative electron op- tics design and novel detectors in con- junction with advances in graphic user interface software allows researchers to expand the use of SEM and provides innovative avenues for data integra- tion and visualization. The highlighted Fig. 5 — Low-kV EDS mapping of graphene film on Ni substrate: data acquired at 1 kV using probe current of 32 nA (top) and data acquired at 5 kV using probe current of 4 nA (bottom). C K Ni L 1kV 5kV