TOWARD A SCANNING ATOM-PROBE - COMPUTER-SIMULATION OF ELECTRIC-FIELD

Development of a new atom probe (AP) named ''scanning atom probe (SAP)'' is proposed. The SAP consists of a funnel-shaped micro-extraction electrode and a thin flat plate grooved or micro-photoetched in a checkerboard pattern, shaping up many micro tips. The extraction electrode scans over the grooved sample surface and stands still above a particular tip forming a minute field emission or field ion microscope with a high field area well confined in a small space between the tip and the electrode. The field distribution in the confined space depends on many factors, setting the configuration and arrangement of the tip and electrode. Accordingly, the field distribution in the confined space is computed in order to find the optimum tip and electrode configuration, and the relative position of them. Variation of the field strength with tip-electrode distances, cone angles of the tip, and the configuration of the electrode, are discussed.