JEOL USA OBF-STEM System (Option)

In the new imaging method 'OBF STEM (Optimum Bright Field STEM)', raw images acquired by a segmented STEM detector are used as the source for a phase image reconstruction, with dedicated Fourier filters to maximize the signal to noise ratio of the retrieved image.

This promising method realizes higher contrast for both heavy and light elements even while operating under extremely low electron dose conditions. Beam sensitive materials which are difficult to observe with standard ADF and ABF STEM methods, can be easily analyzed with higher contrast at a wide range of magnifications using OBF STEM.

K. Ooe, T. Seki, et al., Ultramicroscopy 220, 113133 (2021)

For example, beam sensitive materials including Metal Organic Frameworks (MOFs) and Zeolites require a reduced electron dose (typically, probe current < 1.0 pA) so as not to destroy the framework of light elements while imaging. OBF STEM has an advantage for such low dose experiments, realizing ultra-high dose-efficient STEM imaging at or near atomic resolution.

Both OBF STEM images shown – MOF MIL-101(left) and MFI Zeolite (right) are acquired in a single scan, with the insets showing increased (averaged) resolution and FFT patterns. These examples confirm the usefulness of OBF STEM for obtaining high-resolution and high-contrast images while using a very low dose.

In addition to being highly dose efficient, OBF STEM is also advantageous for light element imaging. Even at a lower acceleration voltage (e.g., 60 kV), both higher contrast and spatial resolution can be achieved for light elements.

In an actual experiment, live OBF imaging is fundamental for beam sensitive materials as all operations should be performed in a dose-limited condition. For enhanced ease-of-use, this live feature is included in the OBF system, implemented within the TEM control software, with simple GUI control and real time display updates alongside conventional STEM images.