Field emission probes
Field emission probes are used in scanning electron microscopy for imaging. When a voltage is applied to these probes, electrons are emitted from the tips through a process known as field electron emission. When a body is subjected to ion milling in vacuum, the geometry of the surface of the body is unknown. Upon further study, the field emission probes will be kept, which will emit electrons as soon as a voltage is applied across it. As a result, this will cause emission of secondary electrons from the surface of the body that is subjected to ion  milling. By collecting these secondary emitted electrons, a clear image of the surface of the ion milled body can be obtained. This is the technique that is used in the scanning electron microscope (SEM). There exist various well-defined techniques for preparing field emission probes. Ideally, a field emission probe should be extremely sharp, possibly terminating in a single atom. In order to resolve details at the atomic level, it should have a small aspect ratio to reduce mechanical vibration while scanning, have a stable atomic configuration at its apex to yield reliable and reproducible images, and be clean to  ensure a stable tunnel junction, since the presence of contaminants like oxides or etching by products could alter its metallic behavior. Our experimental setup helps us obtain tips with an apex radius of a few nanometres. Despite the various well-known methods to make field emission probes, such as the Drop-off method, it is still difficult to get an ideal probe.