Atom Probe

One Dimensional Atom Probe

A kind of microscopy combining time-of-flight spectroscopy and field ion microscopy (FIM).

As in FIM, a sharp tip is made, placed in vacuum at cryogenic temperature ( < 50 K) . A Positive pulsed voltage is applied, causing individual atoms at the surface of the tip to ionize and be repelled from the tip electrostatically. A fast timing circuit is used to measure the time taken between the pulse and the impact of the ion on a detector, thus allowing the mass-to-charge ratio of the ion to be calculated, and thus the element ( or elements) of the ion. From the collection of many of these atoms, a chemical profile of the sample can be made with relative position accuracy of less than one atomic spacing, from a probe size on the order of 1 - 5 nm

Three Dimensional Atom Probe

also called Tomographic Atom Probe (TAP) , 3D Atom Probe (3DAP) , Atom Probe Tomography (APT) , Position Sensitive Atom Probe ( POSAP)

Like One Dimensional Atom Probe, except that a position sensitive detector is used when collecting , and 3D reconstruction can be made of the sample, comprising millions of atoms and volumes of approximately 10 nm x 10 nm x 100 nm

see also Field ion microscope