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)

STEM Low Dose Imaging

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.
Sample : MOF MIL-101
Instrument : JEM-ARM300F2
Accelerating Voltage : 300 kV
Convergence Semi-angle : 7 mrad
Probe current : < 0.15 pA
Insets) FFT pattern and 50 frames averaged image
Sample courtesy of Prof. Zhenxia Zhao, Guangxi University
Sample : MFI Zeolite
JEM-ARM300F2 Eta-corr. FHP2, Acc. 300 kV, alpha = 13 mrad, Probe current = 0.3 pA
Insets) FFT pattern and 10 frames averaged image

High Contrast Imaging for Light Elements

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.
Sample : GaN [110]
Instrument : JEM-ARM200F
Accelerating Voltage : 60 kV
Convergence Semi-angle : 35 mrad
Sample : Graphene
Instrument : JEM-ARM200F
Accelerating Voltage : 60 kV
Convergence Semi-angle : 35 mrad
Sample : β-Si3N4 [0001]
Instrument : JEM-ARM200F
Accelerating Voltage : 200 kV
Convergence Semi-angle : 24 mrad
Inset) 10 frames averaged
Sample : GaN [211]
Instrument : JEM-ARM300F2
Accelerating Voltage : 300 kV
Convergence Semi-angle : 32 mrad
Inset) 20 frames averaged

Live OBF Imaging

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.

Live observation of OBF-STEM images with JEM-ARM200F

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