Читать книгу Amorphous Nanomaterials - Lin Guo - Страница 30

The progress of Cs-TEM has fulfilled the old dream of materials science: a direct link between atomic-level structural information and macroscopic properties. Indeed, people are now able to see the complexities of structure and chemistry at the atomic scale never before, enabling a better understanding of reaction and transformation pathways that fabricated desirable materials and creating new devices with enhanced properties. The use of aberration-corrected TEM is capable of imaging and analyzing materials at the sub-nano resolution in an easily managed way. Moreover, the acquisition of EELS by Cs-TEM can provide distinguishable information about bonding differences between dopant species, which can work with atomic imaging to carry out elemental and chemical analyses of site occupancy. This further paves the way for the study toward physical chemistry at the sub-nanolevel. In addition, based on in-situ TEM equipped with spherical aberration corrector, researchers are good at capturing localized information and inhomogeneity, which opens up the ways for investigating defects in the crystal lattice, charge transport, and phase boundary migration kinetics.

For the future study of Cs-TEM, several improvements are necessary. One is the irreversible structural changes especially at interfaces and surfaces when exposing to the irradiation of highly intense electron beam at higher magnification. This may possibly be alleviated by operating the microscope at a lower voltage or carried out experiments with cryo-TEM. The second is the long-term stability of the aberration corrector; this would require further improvement in corrector hardware to allow aberration control over probe size for longer periods. The third is the sample preparation, which has become more demanding, aiming to eliminate the surface oxide or contamination layers to avoid the background noise to the image signal. For EELS, the aim is to overcome the dechanneling, delocalization, and absorption in electron scattering of each atomic column. In addition, for in situ TEM, more effort should be devoted to high-speed computers for real-time recording to obtain aberration parameters, and then combining faster data acquisition with STEM, which would then open up new chances for three-dimensional tomographic chemical imaging and real-time imaging of STEM-based environmental microscopy in different atmospheres or liquid cells.