ABF (Annular Bright Field) is a STEM imaging mode that collects electrons at small-to-medium scattering angles — providing contrast for both heavy and light elements simultaneously, solving HAADF's limitation of being insensitive to light atoms like oxygen, nitrogen, and lithium.

How Does ABF Work?

• Detector: Annular detector at low-to-medium angles (typically 11-22 mrad for a 22 mrad convergence angle).
• Contrast: Atomic columns appear as dark spots on a bright background (absorptive contrast).
• Light Elements: ABF can image O, N, Li, H columns that are invisible in HAADF.
• Combined: Simultaneously acquire ABF and HAADF for complete heavy + light atom imaging.

Why It Matters

• Light Atom Imaging: The breakthrough that enabled direct imaging of oxygen columns in oxides, nitrogen in nitrides, and lithium in battery materials.
• Complete Structure: HAADF shows cations. ABF shows anions. Together, the complete crystal structure is imaged.
• Battery Materials: Essential for studying lithium-ion battery cathodes where Li positions are critical.

ABF is the light-atom detector — the STEM mode that makes lightweight atoms visible, completing the picture that HAADF alone cannot provide.