What does ABF mean in UNCLASSIFIED

ABF stands for Annular Bright Field, which is an imaging technique used to analyze surface and near-surface features on a sample using bright field illumination.

ABF allows researchers to gain insight into the surface features of a sample such as size, shape, texture and composition. It can also be used to detect defects such as voids or cracks in the material.

The basic principle behind ABF is that the light from a bright field illumination source is focused onto the sample at an angle larger than the critical angle of total reflection for that material. This causes light to reflect off the inner walls of the annular aperture, creating a bright ring of light around the perimeter of the sample which then produces high contrast images.

Annular Bright Field techniques are commonly used in Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and other micro/nano scale descriptive techniques. It has been found to be extremely useful in detecting defects or surface irregularities on samples in order to characterize their mechanical properties or bulk composition. In addition, it can also be useful in determining thicknesses or dimensional measurements at very small scales.

Compared with traditional optical microscopy methods, ABF offers higher resolution and better contrast due to its ability to focus on one plane only instead of scattering light throughout the entire sample volume. Additionally, it avoids optical aberrations while providing results that are more accurate than those obtained with other conventional single plane focused imaging techniques.