Performance of local electrodes in the local electrode atom probe

The use of a local electrode in atom probe tomography has enabled higher rates of data acquisition and increased field of view compared to other variants of three-dimensional atom probes, but specimen fracture can result in damage to the local electrode. Specimens and local electrodes were examined before and after analyses that resulted in specimen failure. Most specimens were found to be melted after failure and as a result, material was found deposited onto the surface of the local electrode. Material transfer from the specimen to the local electrode was verified by energy dispersive spectrometry in a scanning electron microscope. After the fracture of brittle materials, some remnants were found embedded in the local electrode. For either failure mode, it is likely that the primary specimen rupture produced a sharp protrusion on the specimen or local electrode and this triggered an electrical discharge or uncontrolled field emission that melted a portion of the specimen. The lifetime of the local electrode was found to be dependent on the shape and position of the debris from the specimen failure rather than the number of ions collected or the number of specimens characterized. Local electrodes with smaller apertures were found to be more susceptible to failure. (c) 2007 Elsevier B.V. All rights reserved.