Improving data quality for three-dimensional electron diffraction by a post-column energy filter and a new crystal tracking method

• Three-dimensional electron diffraction (3D ED) has become an effective technique to determine the structures of submicrometre- (nanometre-)sized crystals. In this work, energy-filtered 3D ED was implemented using a post-column energy filter in both STEM mode and TEM mode [(S)TEM denoting (scanning) transmission electron microscope]. The setups for performing energy-filtered 3D ED on a Gatan imaging filter are described. The technique and protocol improve the accessibility of energy-filtered 3D ED post-column energy filters, which are available in many TEM laboratories. In addition, a crystal tracking method in STEM mode using high-angle annular dark-field imaging is proposed. This method enables the user to monitor the crystal position while collecting 3D ED data at the same time, allowing a larger tilt range without foregoing any diffraction frames or imposing extra electron dose. In order to compare the differences between energy-filtered and unfiltered 3D ED data sets, three well known crystallized inorganic samples have been studied in detail. For these samples, the final R1 values improved by 10–30% for the energy-filtered data sets compared with the unfiltered data sets, and the structures became more chemically reasonable. Possible reasons for improvement are also discussed.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

post-column energy filters

3D electron diffraction

energy-filtered 3D ED

microcrystal electron diffraction

energy-filtered MicroED

HAADF

crystal tracking

structure determination

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