Ultrahigh Resolution of Electron Energy Loss Spectroscopy by a Monochromated Titan TEM: Towards Challenging Nanomaterials Characterization

Electron Energy Loss Spectroscopy (EELS) applied in Transmission Electron Microcopy (TEM) is a powerful analytical technique for the characterization of modern nano-materials. This technique is especially useful when TEM system is equipped with a monochromator of electron source or electron gun (to minimize the energy speared inherent to electron emission process). The majority of available monochromated TEMs (e.g. FEI’s Titan) has the energy resolution in the range of 150-200meV. However, for a considerable number of scientific challenges the key characteristic features of EELS measurements require the resolution better than 50meV. Among those challenges are the vibrational spectroscopy for inorganic and organic materials, including the detection of hydrogen [1], measurement of phonons distribution or bandgap states with high spatial resolution [2], and study of Van der Waals materials exhibiting intriguing structural, electronic and photonic properties [3]. Recently a significant progress is achieved in EELS-TEM systems performance. This progress is mainly associated with a monochromated scanning TEM (STEM) developed by NION Co, with a regular energy resolution of about 10meV [1]. At the same time, it has been predicted theoretically, that the original design of FEI’s monochromator could deliver a comparable energy resolution (16meV) subject to the availability of a high resolution energy detection system [4].