Focused Ion Beam (FIB) is a setup similar to a scanning electron beam, but with a beam of ions instead. Currently, the most used is the gallium ion beam powered by liquid metal ion sources (LMIS). The FIB can be accelerated to 0.5-30 kV with current up to 100 nA.
Ion Beam Milling
The most important application of FIB is to mill into samples: the accelerated ions attack the sample surface, remove the atoms from the material with a controlled dwell time and dose, therefore a volume is taken away from the sample revealing a section in depth which is ready to be imaged and analysed. Due to this nature, the removed material from the sample cannot be restored. Besides, gallium implants into the sample may occur during the milling process which should be made aware of in case of sensitive materials.
With the milling capability of FIB, in-depth structures are exposed which cannot be seen from the top surface.
Ion Beam Deposition
With the assistance of Gas Injection System, more functions can be achieved such as in-situ deposition for conductive pathway establishment and protection of the region of interest, gas-assisted enhanced etching on silicon-based semiconductor materials, and local charge compensation on non-conductive samples.
The image on the right shows a layer of platinium that has been deposited on the sample, which will help protect the area underneath and reduce the curtaining effect during cross-section imaging and serial sectioning tomography acquisition.
Ion Beam Imaging
The gallium ion beam can be used to generate images in a way similar to SEM and offers great grain orientation contrast in crystalline materials, along with great atomic number contrast.
The image on the right shows an ion beam image on a cross-section of an electroplated tin on brass sample, with an electron image as inset taken from exactly the same area.