Applications of direct detection device in transmission electron microscopy

Abstract

A prototype Direct Detection Device (DDD) camera system has shown great promise in improving both the spatial resolution and the signal to noise ratio for electron microscopy at 120-400 keV beam energies (Xuong, et al., 2007. Methods in Cell Biology, 79, 721-739). Without the need for a resolution-limiting scintillation screen as in the charge coupled device (CCD), the DDD camera can outperform CCD based systems in terms of spatial resolution, due to its small pixel size (5 μm). In this paper, the modulation transfer function (MTF) of the DDD prototype is measured and compared with the specifications of commercial scientific CCD camera systems. Combining the fast speed of the DDD with image mosaic techniques, fast wide-area imaging is now possible. In this paper, the first large area mosaic image and the first tomography dataset from the DDD camera are presented, along with an image processing algorithm to correct the specimen drift utilizing the fast readout of the DDD system.

Scanning transmission electron microscopy strain measurement from millisecond frames of a direct electron charge coupled device

“…This extends the scope of application for direct electron detectors, whose excellent detection quantum efficiency and signal-to-noise ratio have as yet enhanced nearly uniquely low-dose applications as used for biological imaging. [23][24][25][26][27] In this study, we used 300 keV electrons as the microscope performs best at this energy as to STEM probe formation. However, it can be expected that lowering the TEM acceleration voltage to less than 100 kV will lead to a strong improvement of the camera's point spread function, from which both SANBED and conventional TEM applications will profit.…”

Numerical geometry of map and model assessment

“…Modern CMOS detectors combined with movie frame stacking have eliminated much of the specimen drift that has limited cryo-EM imaging using earlier detectors. The new direct detection camera technology is a major breakthrough toward higher-resolution cryo-EM reconstruction (Jin et al, 2008). The new imaging techniques enable the production of many 3D density maps that, at the highest resolution end of the scale (better than 3.4 Å), allow atomic structures to be solved directly.…”

High resolution single particle refinement in EMAN2.1

“…Similarly, if there were any specimen charging or a significant amount of astigmatism, the images would also be discarded. With the development of direct detectors [11], a single exposure is now often subdivided into many frames forming a ‘movie’ with up to ~100 frames. By aligning the frames before averaging to produce a ‘micrograph’, it is often possible to eliminate the majority of the drift which was previously a large problem[12].…”