Direct Detection Electron Energy-Loss Spectroscopy: A Method to Push the Limits of Resolution and Sensitivity

Abstract

In many cases, electron counting with direct detection sensors offers improved resolution, lower noise, and higher pixel density compared to conventional, indirect detection sensors for electron microscopy applications. Direct detection technology has previously been utilized, with great success, for imaging and diffraction, but potential advantages for spectroscopy remain unexplored. Here we compare the performance of a direct detection sensor operated in counting mode and an indirect detection sensor (scintillator/fiber-optic/CCD) for electron energy-loss spectroscopy. Clear improvements in measured detective quantum efficiency and combined energy resolution/energy field-of-view are offered by counting mode direct detection, showing promise for efficient spectrum imaging, low-dose mapping of beam-sensitive specimens, trace element analysis, and time-resolved spectroscopy. Despite the limited counting rate imposed by the readout electronics, we show that both core-loss and low-loss spectral acquisition are practical. These developments will benefit biologists, chemists, physicists, and materials scientists alike.

Localized corrosion of low-carbon steel at the nanoscale

“…New hardware and techniques are being implemented to obtain real-time compositional information from materials within the LC-STEM concurrent with in-situ observation. 23,31 Nanoscale corrosion pathways, like the one identified in this work, could have a profound impact on the degradation behavior of bulk materials. This work suggests that the types of electrochemically active interfaces that typify and pervade the steel microstructure may participate in accelerated corrosion mechanisms that, extrapolated to the bulk-scale, would create percolation networks that expose the interior body of the steel to corrosive conditions much sooner than predicted by uniform corrosion models.…”

“…Further understanding of the corrosion product deposition mechanisms could be achieved by implementing new instrumentation and methods that are complementary to in-situ TEM and that enable tracking of the iron oxide evolution in-situ. 22,31 Overlaying the initial grain boundary outline onto the postmortem image (Fig. 4a, b) revealed that the cementite grain had moved relative to its initial position (confirmed via TEM and spot diffraction analysis), rotating from its initial 25 degrees to a final 20 degrees relative to the fluid flow direction (Fig.…”

Measurement of the Indirect Band Gap of Diamond with EELS in STEM

“…Signal to noise ratio remains an open issue when acquiring spectra far outside the CBED disks. The current manuscript shows, that acceptable signal levels can be obtained, and progress in single electron detectors, is providing an attractive route to further improve the signal to noise ratio and open a new era of band structure studies with EELS in TEM …”

Optimally Sharp Energy Filtering of Quantum Particles via Homogeneous Planar Inclusions

“…Moreover, systematic efforts towards filter design based on matter waves interference into potential superlattices by manipulating the emerged resonances have been recorded 24 , with the obtained results being experimentally tested 25 . Since then, interference-based energy filters have been used to perform very accurate scanning tunneling spectroscopic measurements 26 and to execute electron counting with high resolution and sensitivity 27 . Most significantly, similar potential distributions with increased selectivity have played the role of modules in interferometric experiments complementing the field of electron holography 28 and controlling the quantum transport phenomena in nanoscale systems via time -dependent fields 29 .…”