Focused ion beam (FIB) technology
This technology involves using an ion beam (typically gallium ions) directed onto a hard sample. The beam is focussed to an extremely fine probe size (<10 nm) onto the surface of a specimen. The sample can be sectioned or shaped with the ion beam while it is being monitored by scanning electron microscopy (SEM). FIB can cut 10-nm-thick sections from very hard materials. These sections can be taken off as sequential sections, each viewed in turn with the SEM mode, and this imaging information used to construct a 3D image. FIB can also be used to shape needles that can then be viewed by other techniques such as transmission electron microscopy or atom probe tomography. It can also be used for deposition of materials in a small area (approx 100nm) from chemical vapour from specific gasses.
When milling a region or cutting a piece out of a sample, it is important to firstly lay down a strip of metal that will stop the ion beam from eroding that region. This allows a well defined edge to be achieved on the area being excised.
Machines can have both ion and electron columns on a single instrument (called dual beam instruments). The advantage of dual beam machines is that they allow specimens to be imaged in detail using the electron beam, without damaging the surface of the specimen with the ion beam.